diff --git a/Cargo.toml b/Cargo.toml
index 9a6c0fc5ad88d..5fe7da2a416e2 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -191,8 +191,8 @@ name = "custom_diagnostic"
 path = "examples/diagnostics/custom_diagnostic.rs"
 
 [[example]]
-name = "print_diagnostics"
-path = "examples/diagnostics/print_diagnostics.rs"
+name = "log_diagnostics"
+path = "examples/diagnostics/log_diagnostics.rs"
 
 [[example]]
 name = "event"
diff --git a/crates/bevy_asset/Cargo.toml b/crates/bevy_asset/Cargo.toml
index e5644853e567b..1b8a01e6a3bf6 100644
--- a/crates/bevy_asset/Cargo.toml
+++ b/crates/bevy_asset/Cargo.toml
@@ -19,6 +19,7 @@ filesystem_watcher = ["notify"]
 [dependencies]
 # bevy
 bevy_app = { path = "../bevy_app", version = "0.4.0" }
+bevy_diagnostic = { path = "../bevy_diagnostic", version = "0.4.0" }
 bevy_ecs = { path = "../bevy_ecs", version = "0.4.0" }
 bevy_reflect = { path = "../bevy_reflect", version = "0.4.0", features = ["bevy"] }
 bevy_tasks = { path = "../bevy_tasks", version = "0.4.0" }
diff --git a/crates/bevy_asset/src/diagnostic/asset_count_diagnostics_plugin.rs b/crates/bevy_asset/src/diagnostic/asset_count_diagnostics_plugin.rs
new file mode 100644
index 0000000000000..db3d773d5004d
--- /dev/null
+++ b/crates/bevy_asset/src/diagnostic/asset_count_diagnostics_plugin.rs
@@ -0,0 +1,35 @@
+use crate::{Asset, Assets};
+use bevy_app::prelude::*;
+use bevy_diagnostic::{Diagnostic, DiagnosticId, Diagnostics};
+use bevy_ecs::{IntoSystem, Res, ResMut};
+
+/// Adds "asset count" diagnostic to an App
+#[derive(Default)]
+pub struct AssetCountDiagnosticsPlugin<T: Asset> {
+    marker: std::marker::PhantomData<T>,
+}
+
+impl<T: Asset> Plugin for AssetCountDiagnosticsPlugin<T> {
+    fn build(&self, app: &mut AppBuilder) {
+        app.add_startup_system(Self::setup_system.system())
+            .add_system(Self::diagnostic_system.system());
+    }
+}
+
+impl<T: Asset> AssetCountDiagnosticsPlugin<T> {
+    pub fn diagnostic_id() -> DiagnosticId {
+        DiagnosticId(T::TYPE_UUID)
+    }
+
+    pub fn setup_system(mut diagnostics: ResMut<Diagnostics>) {
+        diagnostics.add(Diagnostic::new(
+            Self::diagnostic_id(),
+            &format!("asset_count {}", std::any::type_name::<T>()),
+            20,
+        ));
+    }
+
+    pub fn diagnostic_system(mut diagnostics: ResMut<Diagnostics>, assets: Res<Assets<T>>) {
+        diagnostics.add_measurement(Self::diagnostic_id(), assets.len() as f64);
+    }
+}
diff --git a/crates/bevy_asset/src/diagnostic/mod.rs b/crates/bevy_asset/src/diagnostic/mod.rs
new file mode 100644
index 0000000000000..f093527f9755a
--- /dev/null
+++ b/crates/bevy_asset/src/diagnostic/mod.rs
@@ -0,0 +1,2 @@
+mod asset_count_diagnostics_plugin;
+pub use asset_count_diagnostics_plugin::AssetCountDiagnosticsPlugin;
diff --git a/crates/bevy_asset/src/lib.rs b/crates/bevy_asset/src/lib.rs
index 5c9b4133b9d81..e65ce22bd0c39 100644
--- a/crates/bevy_asset/src/lib.rs
+++ b/crates/bevy_asset/src/lib.rs
@@ -1,5 +1,6 @@
 mod asset_server;
 mod assets;
+pub mod diagnostic;
 #[cfg(all(
     feature = "filesystem_watcher",
     all(not(target_arch = "wasm32"), not(target_os = "android"))
diff --git a/crates/bevy_diagnostic/Cargo.toml b/crates/bevy_diagnostic/Cargo.toml
index 2b39528e295ef..c96f967c05f0e 100644
--- a/crates/bevy_diagnostic/Cargo.toml
+++ b/crates/bevy_diagnostic/Cargo.toml
@@ -18,6 +18,7 @@ keywords = ["bevy"]
 bevy_app = { path = "../bevy_app", version = "0.4.0" }
 bevy_core = { path = "../bevy_core", version = "0.4.0" }
 bevy_ecs = { path = "../bevy_ecs", version = "0.4.0" }
+bevy_log = { path = "../bevy_log", version = "0.4.0" }
 bevy_utils = { path = "../bevy_utils", version = "0.4.0" }
 
 # other
diff --git a/crates/bevy_diagnostic/src/diagnostic.rs b/crates/bevy_diagnostic/src/diagnostic.rs
index 20d7edcf93e3e..549ecdb20f755 100644
--- a/crates/bevy_diagnostic/src/diagnostic.rs
+++ b/crates/bevy_diagnostic/src/diagnostic.rs
@@ -1,8 +1,8 @@
 use bevy_utils::{Duration, HashMap, Instant, Uuid};
-use std::collections::VecDeque;
+use std::collections::{BTreeSet, VecDeque};
 
 /// Unique identifier for a [Diagnostic]
-#[derive(Debug, Copy, Clone, Hash, Eq, PartialEq)]
+#[derive(Debug, Copy, Clone, Hash, Eq, PartialEq, PartialOrd, Ord)]
 pub struct DiagnosticId(pub Uuid);
 
 impl DiagnosticId {
@@ -102,10 +102,12 @@ impl Diagnostic {
 #[derive(Debug, Default)]
 pub struct Diagnostics {
     diagnostics: HashMap<DiagnosticId, Diagnostic>,
+    ordered_diagnostics: BTreeSet<DiagnosticId>,
 }
 
 impl Diagnostics {
     pub fn add(&mut self, diagnostic: Diagnostic) {
+        self.ordered_diagnostics.insert(diagnostic.id);
         self.diagnostics.insert(diagnostic.id, diagnostic);
     }
 
@@ -132,4 +134,10 @@ impl Diagnostics {
     pub fn iter(&self) -> impl Iterator<Item = &Diagnostic> {
         self.diagnostics.values()
     }
+
+    pub fn ordered_iter(&self) -> impl Iterator<Item = &Diagnostic> {
+        self.ordered_diagnostics
+            .iter()
+            .filter_map(move |k| self.diagnostics.get(k))
+    }
 }
diff --git a/crates/bevy_diagnostic/src/entity_count_diagnostics_plugin.rs b/crates/bevy_diagnostic/src/entity_count_diagnostics_plugin.rs
new file mode 100644
index 0000000000000..36a709f453795
--- /dev/null
+++ b/crates/bevy_diagnostic/src/entity_count_diagnostics_plugin.rs
@@ -0,0 +1,29 @@
+use crate::{Diagnostic, DiagnosticId, Diagnostics};
+use bevy_app::prelude::*;
+use bevy_ecs::{IntoSystem, ResMut, Resources, World};
+
+/// Adds "entity count" diagnostic to an App
+#[derive(Default)]
+pub struct EntityCountDiagnosticsPlugin;
+
+impl Plugin for EntityCountDiagnosticsPlugin {
+    fn build(&self, app: &mut AppBuilder) {
+        app.add_startup_system(Self::setup_system.system())
+            .add_system(Self::diagnostic_system.system());
+    }
+}
+
+impl EntityCountDiagnosticsPlugin {
+    pub const ENTITY_COUNT: DiagnosticId =
+        DiagnosticId::from_u128(187513512115068938494459732780662867798);
+
+    pub fn setup_system(mut diagnostics: ResMut<Diagnostics>) {
+        diagnostics.add(Diagnostic::new(Self::ENTITY_COUNT, "entity_count", 20));
+    }
+
+    pub fn diagnostic_system(world: &mut World, resources: &mut Resources) {
+        if let Some(mut diagnostics) = resources.get_mut::<Diagnostics>() {
+            diagnostics.add_measurement(Self::ENTITY_COUNT, world.entity_count() as f64);
+        }
+    }
+}
diff --git a/crates/bevy_diagnostic/src/lib.rs b/crates/bevy_diagnostic/src/lib.rs
index d54c32663ca62..dfb6b6d324e4f 100644
--- a/crates/bevy_diagnostic/src/lib.rs
+++ b/crates/bevy_diagnostic/src/lib.rs
@@ -1,9 +1,11 @@
 mod diagnostic;
+mod entity_count_diagnostics_plugin;
 mod frame_time_diagnostics_plugin;
-mod print_diagnostics_plugin;
+mod log_diagnostics_plugin;
 pub use diagnostic::*;
+pub use entity_count_diagnostics_plugin::EntityCountDiagnosticsPlugin;
 pub use frame_time_diagnostics_plugin::FrameTimeDiagnosticsPlugin;
-pub use print_diagnostics_plugin::PrintDiagnosticsPlugin;
+pub use log_diagnostics_plugin::LogDiagnosticsPlugin;
 
 use bevy_app::prelude::*;
 
diff --git a/crates/bevy_diagnostic/src/print_diagnostics_plugin.rs b/crates/bevy_diagnostic/src/log_diagnostics_plugin.rs
similarity index 55%
rename from crates/bevy_diagnostic/src/print_diagnostics_plugin.rs
rename to crates/bevy_diagnostic/src/log_diagnostics_plugin.rs
index e71f4b9066634..276480786f611 100644
--- a/crates/bevy_diagnostic/src/print_diagnostics_plugin.rs
+++ b/crates/bevy_diagnostic/src/log_diagnostics_plugin.rs
@@ -2,24 +2,25 @@ use super::{Diagnostic, DiagnosticId, Diagnostics};
 use bevy_app::prelude::*;
 use bevy_core::{Time, Timer};
 use bevy_ecs::{IntoSystem, Res, ResMut};
+use bevy_log::{debug, info};
 use bevy_utils::Duration;
 
-/// An App Plugin that prints diagnostics to the console
-pub struct PrintDiagnosticsPlugin {
+/// An App Plugin that logs diagnostics to the console
+pub struct LogDiagnosticsPlugin {
     pub debug: bool,
     pub wait_duration: Duration,
     pub filter: Option<Vec<DiagnosticId>>,
 }
 
-/// State used by the [PrintDiagnosticsPlugin]
-pub struct PrintDiagnosticsState {
+/// State used by the [LogDiagnosticsPlugin]
+struct LogDiagnosticsState {
     timer: Timer,
     filter: Option<Vec<DiagnosticId>>,
 }
 
-impl Default for PrintDiagnosticsPlugin {
+impl Default for LogDiagnosticsPlugin {
     fn default() -> Self {
-        PrintDiagnosticsPlugin {
+        LogDiagnosticsPlugin {
             debug: false,
             wait_duration: Duration::from_secs(1),
             filter: None,
@@ -27,9 +28,9 @@ impl Default for PrintDiagnosticsPlugin {
     }
 }
 
-impl Plugin for PrintDiagnosticsPlugin {
+impl Plugin for LogDiagnosticsPlugin {
     fn build(&self, app: &mut bevy_app::AppBuilder) {
-        app.add_resource(PrintDiagnosticsState {
+        app.add_resource(LogDiagnosticsState {
             timer: Timer::new(self.wait_duration, true),
             filter: self.filter.clone(),
         });
@@ -37,68 +38,66 @@ impl Plugin for PrintDiagnosticsPlugin {
         if self.debug {
             app.add_system_to_stage(
                 stage::POST_UPDATE,
-                Self::print_diagnostics_debug_system.system(),
+                Self::log_diagnostics_debug_system.system(),
             );
         } else {
-            app.add_system_to_stage(stage::POST_UPDATE, Self::print_diagnostics_system.system());
+            app.add_system_to_stage(stage::POST_UPDATE, Self::log_diagnostics_system.system());
         }
     }
 }
 
-impl PrintDiagnosticsPlugin {
+impl LogDiagnosticsPlugin {
     pub fn filtered(filter: Vec<DiagnosticId>) -> Self {
-        PrintDiagnosticsPlugin {
+        LogDiagnosticsPlugin {
             filter: Some(filter),
             ..Default::default()
         }
     }
 
-    fn print_diagnostic(diagnostic: &Diagnostic) {
+    fn log_diagnostic(diagnostic: &Diagnostic) {
         if let Some(value) = diagnostic.value() {
-            print!("{:<65}: {:<10.6}", diagnostic.name, value);
             if let Some(average) = diagnostic.average() {
-                print!("  (avg {:.6})", average);
+                info!(
+                    "{:<65}: {:<10.6}  (avg {:.6})",
+                    diagnostic.name, value, average
+                );
+            } else {
+                info!("{:<65}: {:<10.6}", diagnostic.name, value);
             }
-
-            println!("\n");
         }
     }
 
-    pub fn print_diagnostics_system(
-        mut state: ResMut<PrintDiagnosticsState>,
+    fn log_diagnostics_system(
+        mut state: ResMut<LogDiagnosticsState>,
         time: Res<Time>,
         diagnostics: Res<Diagnostics>,
     ) {
         if state.timer.tick(time.delta_seconds()).finished() {
-            println!("Diagnostics:");
-            println!("{}", "-".repeat(93));
             if let Some(ref filter) = state.filter {
                 for diagnostic in filter.iter().map(|id| diagnostics.get(*id).unwrap()) {
-                    Self::print_diagnostic(diagnostic);
+                    Self::log_diagnostic(diagnostic);
                 }
             } else {
-                for diagnostic in diagnostics.iter() {
-                    Self::print_diagnostic(diagnostic);
+                for diagnostic in diagnostics.ordered_iter() {
+                    Self::log_diagnostic(diagnostic);
                 }
             }
         }
     }
 
-    pub fn print_diagnostics_debug_system(
-        mut state: ResMut<PrintDiagnosticsState>,
+    fn log_diagnostics_debug_system(
+        mut state: ResMut<LogDiagnosticsState>,
         time: Res<Time>,
         diagnostics: Res<Diagnostics>,
     ) {
         if state.timer.tick(time.delta_seconds()).finished() {
-            println!("Diagnostics (Debug):");
-            println!("{}", "-".repeat(93));
             if let Some(ref filter) = state.filter {
                 for diagnostic in filter.iter().map(|id| diagnostics.get(*id).unwrap()) {
-                    println!("{:#?}\n", diagnostic);
+                    debug!("{:#?}\n", diagnostic);
                 }
             } else {
-                for diagnostic in diagnostics.iter() {
-                    println!("{:#?}\n", diagnostic);
+                for diagnostic in diagnostics.ordered_iter() {
+                    debug!("{:#?}\n", diagnostic);
                 }
             }
         }
diff --git a/crates/bevy_ecs/src/core/entities.rs b/crates/bevy_ecs/src/core/entities.rs
index 146856f4ea4fb..f7d001cae7c40 100644
--- a/crates/bevy_ecs/src/core/entities.rs
+++ b/crates/bevy_ecs/src/core/entities.rs
@@ -252,9 +252,20 @@ impl Entities {
         }
     }
 
+    /// Number of freed entities in `self.meta`
+    pub fn freed_len(&self) -> u32 {
+        self.free_cursor.load(Ordering::Relaxed)
+    }
+
+    /// Number of reserved entities outside of `self.meta`
+    pub fn pending_len(&self) -> u32 {
+        self.pending.load(Ordering::Relaxed)
+    }
+
     // The following three methods allow iteration over `reserved` simultaneous to location
     // writes. This is a lazy hack, but we only use it in `World::flush` so the complexity and unsafety
     // involved in producing an `impl Iterator<Item=(u32, &mut Location)>` isn't a clear win.
+    /// Number of reserved entities in `self.meta`
     pub fn reserved_len(&self) -> u32 {
         self.reserved_cursor.load(Ordering::Relaxed)
     }
diff --git a/crates/bevy_ecs/src/core/world.rs b/crates/bevy_ecs/src/core/world.rs
index ca0c2938f0976..b7adb54a978a1 100644
--- a/crates/bevy_ecs/src/core/world.rs
+++ b/crates/bevy_ecs/src/core/world.rs
@@ -500,6 +500,12 @@ impl World {
         })
     }
 
+    pub fn entity_count(&self) -> u32 {
+        self.entities.meta.len() as u32 - self.entities.freed_len()
+            + self.entities.reserved_len()
+            + self.entities.pending_len()
+    }
+
     /// Borrow the `T` component of `entity` without checking if it can be mutated
     ///
     /// # Safety
diff --git a/examples/3d/spawner.rs b/examples/3d/spawner.rs
index c2a5c7f045619..581776c355815 100644
--- a/examples/3d/spawner.rs
+++ b/examples/3d/spawner.rs
@@ -1,5 +1,5 @@
 use bevy::{
-    diagnostic::{FrameTimeDiagnosticsPlugin, PrintDiagnosticsPlugin},
+    diagnostic::{FrameTimeDiagnosticsPlugin, LogDiagnosticsPlugin},
     prelude::*,
 };
 use rand::{rngs::StdRng, Rng, SeedableRng};
@@ -12,7 +12,7 @@ fn main() {
     App::build()
         .add_plugins(DefaultPlugins)
         .add_plugin(FrameTimeDiagnosticsPlugin::default())
-        .add_plugin(PrintDiagnosticsPlugin::default())
+        .add_plugin(LogDiagnosticsPlugin::default())
         .add_startup_system(setup.system())
         .add_system(move_cubes.system())
         .run();
diff --git a/examples/README.md b/examples/README.md
index ae229238f9776..16a8b4d212427 100644
--- a/examples/README.md
+++ b/examples/README.md
@@ -108,7 +108,7 @@ Example | File | Description
 Example | File | Description
 --- | --- | ---
 `custom_diagnostic` | [`diagnostics/custom_diagnostic.rs`](./diagnostics/custom_diagnostic.rs) | Shows how to create a custom diagnostic
-`print_diagnostics` | [`diagnostics/print_diagnostics.rs`](./diagnostics/print_diagnostics.rs) | Add a plugin that prints diagnostics to the console
+`log_diagnostics` | [`diagnostics/log_diagnostics.rs`](./diagnostics/log_diagnostics.rs) | Add a plugin that logs diagnostics to the console
 
 ## ECS (Entity Component System)
 
diff --git a/examples/app/plugin_group.rs b/examples/app/plugin_group.rs
index 81cd0b2ef2201..7e0be8143b6b3 100644
--- a/examples/app/plugin_group.rs
+++ b/examples/app/plugin_group.rs
@@ -11,7 +11,7 @@ fn main() {
         // .add_plugins_with(HelloWorldPlugins, |group| {
         //     group
         //         .disable::<PrintWorldPlugin>()
-        //         .add_before::<PrintHelloPlugin, _>(bevy::diagnostic::PrintDiagnosticsPlugin::default())
+        //         .add_before::<PrintHelloPlugin, _>(bevy::diagnostic::LogDiagnosticsPlugin::default())
         // })
         .run();
 }
diff --git a/examples/diagnostics/custom_diagnostic.rs b/examples/diagnostics/custom_diagnostic.rs
index 4b2e832467a44..ea2eb59123eb5 100644
--- a/examples/diagnostics/custom_diagnostic.rs
+++ b/examples/diagnostics/custom_diagnostic.rs
@@ -1,5 +1,5 @@
 use bevy::{
-    diagnostic::{Diagnostic, DiagnosticId, Diagnostics, PrintDiagnosticsPlugin},
+    diagnostic::{Diagnostic, DiagnosticId, Diagnostics, LogDiagnosticsPlugin},
     prelude::*,
 };
 
@@ -8,7 +8,7 @@ fn main() {
     App::build()
         .add_plugins(DefaultPlugins)
         // The "print diagnostics" plugin is optional. It just visualizes our diagnostics in the console
-        .add_plugin(PrintDiagnosticsPlugin::default())
+        .add_plugin(LogDiagnosticsPlugin::default())
         .add_startup_system(setup_diagnostic_system.system())
         .add_system(my_system.system())
         .run();
diff --git a/examples/diagnostics/print_diagnostics.rs b/examples/diagnostics/log_diagnostics.rs
similarity index 53%
rename from examples/diagnostics/print_diagnostics.rs
rename to examples/diagnostics/log_diagnostics.rs
index 5ed9a5f108109..a48efde05623f 100644
--- a/examples/diagnostics/print_diagnostics.rs
+++ b/examples/diagnostics/log_diagnostics.rs
@@ -1,5 +1,5 @@
 use bevy::{
-    diagnostic::{FrameTimeDiagnosticsPlugin, PrintDiagnosticsPlugin},
+    diagnostic::{FrameTimeDiagnosticsPlugin, LogDiagnosticsPlugin},
     prelude::*,
 };
 
@@ -9,9 +9,13 @@ fn main() {
         // Adds frame time diagnostics
         .add_plugin(FrameTimeDiagnosticsPlugin::default())
         // Adds a system that prints diagnostics to the console
-        .add_plugin(PrintDiagnosticsPlugin::default())
+        .add_plugin(LogDiagnosticsPlugin::default())
         // Any plugin can register diagnostics
         // Uncomment this to add some render resource diagnostics:
         // .add_plugin(bevy::wgpu::diagnostic::WgpuResourceDiagnosticsPlugin::default())
+        // Uncomment this to add an entity count diagnostics:
+        // .add_plugin(bevy::diagnostic::EntityCountDiagnosticsPlugin::default())
+        // Uncomment this to add an asset count diagnostics:
+        // .add_plugin(bevy::asset::diagnostic::AssetCountDiagnosticsPlugin::<Texture>::default())
         .run();
 }