diff --git a/packages/fast-element/docs/roadmap.md b/packages/fast-element/docs/roadmap.md
index 839f0fcf131..815a2de4dac 100644
--- a/packages/fast-element/docs/roadmap.md
+++ b/packages/fast-element/docs/roadmap.md
@@ -2,8 +2,6 @@
 
 ## Short-term
 
-* **Fix**: Improve subscription cleanup on complex observable expressions.
-* **Feature**: ElementStyle Registration and Behavior Association.
 * **Feature**: Support `class` and/or `style` bindings on the host.
 * **Test**: Testing infrastructure and test coverage.
 
diff --git a/packages/fast-element/src/controller.ts b/packages/fast-element/src/controller.ts
index 2b4660a6935..dbc4578de7d 100644
--- a/packages/fast-element/src/controller.ts
+++ b/packages/fast-element/src/controller.ts
@@ -3,6 +3,8 @@ import { Container, InterfaceSymbol, Registry, Resolver } from "./di";
 import { ElementView } from "./view";
 import { PropertyChangeNotifier } from "./observation/notifier";
 import { Observable } from "./observation/observable";
+import { Behavior } from "./directives/behavior";
+import { ElementStyles, StyleTarget } from "./styles";
 
 const defaultEventOptions: CustomEventInit = {
     bubbles: true,
@@ -14,6 +16,7 @@ export class Controller extends PropertyChangeNotifier implements Container {
     public isConnected: boolean = false;
     private resolvers: Map<any, Resolver> = new Map<any, Resolver>();
     private boundObservables: Record<string, any> | null = null;
+    private behaviors: Behavior[] | null = null;
 
     public constructor(
         public readonly element: HTMLElement,
@@ -38,8 +41,8 @@ export class Controller extends PropertyChangeNotifier implements Container {
             }
         }
 
-        if (styles !== void 0 && shadowRoot !== void 0) {
-            styles.applyTo(shadowRoot);
+        if (styles !== void 0) {
+            this.addStyles(styles, shadowRoot);
         }
 
         definition.dependencies.forEach((x: Registry) => x.register(this));
@@ -65,6 +68,78 @@ export class Controller extends PropertyChangeNotifier implements Container {
         }
     }
 
+    public addStyles(
+        styles: ElementStyles,
+        target: StyleTarget | null = this.element.shadowRoot
+    ): void {
+        if (target !== null) {
+            styles.addStylesTo(target);
+        }
+
+        const sourceBehaviors = styles.behaviors;
+
+        if (sourceBehaviors !== null) {
+            this.addBehaviors(sourceBehaviors);
+        }
+    }
+
+    public removeStyles(styles: ElementStyles): void {
+        const target = this.element.shadowRoot;
+
+        if (target !== null) {
+            styles.removeStylesFrom(target);
+        }
+
+        const sourceBehaviors = styles.behaviors;
+
+        if (sourceBehaviors !== null) {
+            this.removeBehaviors(sourceBehaviors);
+        }
+    }
+
+    public addBehaviors(behaviors: ReadonlyArray<Behavior>): void {
+        const targetBehaviors = this.behaviors || (this.behaviors = []);
+        const length = behaviors.length;
+
+        for (let i = 0; i < length; ++i) {
+            targetBehaviors.push(behaviors[i]);
+        }
+
+        if (this.isConnected) {
+            const element = this.element;
+
+            for (let i = 0; i < length; ++i) {
+                behaviors[i].bind(element);
+            }
+        }
+    }
+
+    public removeBehaviors(behaviors: ReadonlyArray<Behavior>): void {
+        const targetBehaviors = this.behaviors;
+
+        if (targetBehaviors === null) {
+            return;
+        }
+
+        const length = behaviors.length;
+
+        for (let i = 0; i < length; ++i) {
+            const index = targetBehaviors.indexOf(behaviors[i]);
+
+            if (index !== -1) {
+                targetBehaviors.splice(index, 1);
+            }
+        }
+
+        if (this.isConnected) {
+            const element = this.element;
+
+            for (let i = 0; i < length; ++i) {
+                behaviors[i].unbind(element);
+            }
+        }
+    }
+
     public onConnectedCallback(): void {
         if (this.isConnected) {
             return;
@@ -85,8 +160,18 @@ export class Controller extends PropertyChangeNotifier implements Container {
             this.boundObservables = null;
         }
 
-        if (this.view !== null) {
-            this.view.bind(element);
+        const view = this.view;
+
+        if (view !== null) {
+            view.bind(element);
+        }
+
+        const behaviors = this.behaviors;
+
+        if (behaviors !== null) {
+            for (let i = 0, ii = behaviors.length; i < ii; ++i) {
+                behaviors[i].bind(element);
+            }
         }
 
         this.isConnected = true;
@@ -99,8 +184,20 @@ export class Controller extends PropertyChangeNotifier implements Container {
 
         this.isConnected = false;
 
-        if (this.view !== null) {
-            this.view.unbind();
+        const view = this.view;
+
+        if (view !== null) {
+            view.unbind();
+        }
+
+        const behaviors = this.behaviors;
+
+        if (behaviors !== null) {
+            const element = this.element;
+
+            for (let i = 0, ii = behaviors.length; i < ii; ++i) {
+                behaviors[i].unbind(element);
+            }
         }
     }
 
diff --git a/packages/fast-element/src/directives/behavior.ts b/packages/fast-element/src/directives/behavior.ts
index b39e6a51c98..0d543399aea 100644
--- a/packages/fast-element/src/directives/behavior.ts
+++ b/packages/fast-element/src/directives/behavior.ts
@@ -1,6 +1,6 @@
 export interface Behavior {
     bind(source: unknown): void;
-    unbind(): void;
+    unbind(source: unknown): void;
 }
 
 export interface BehaviorFactory {
diff --git a/packages/fast-element/src/observation/array-change-records.ts b/packages/fast-element/src/observation/array-change-records.ts
index ef960fd4b89..bbaf3cb6bb7 100644
--- a/packages/fast-element/src/observation/array-change-records.ts
+++ b/packages/fast-element/src/observation/array-change-records.ts
@@ -208,7 +208,7 @@ export function calcSplices(
     old: any[],
     oldStart: number,
     oldEnd: number
-): readonly never[] | Splice[] {
+): ReadonlyArray<never> | Splice[] {
     let prefixCount = 0;
     let suffixCount = 0;
 
diff --git a/packages/fast-element/src/styles.ts b/packages/fast-element/src/styles.ts
index c16dcf7622c..99ffbf9a1b1 100644
--- a/packages/fast-element/src/styles.ts
+++ b/packages/fast-element/src/styles.ts
@@ -1,35 +1,86 @@
-const elementStylesBrand = Symbol();
+import { Behavior } from "./directives/behavior";
 
-export interface ElementStyles {
-    readonly styles: InjectableStyles[];
-    applyTo(shadowRoot: ShadowRoot): void;
+export interface StyleTarget {
+    adoptedStyleSheets?: CSSStyleSheet[];
+
+    prepend(node: Node): void;
+    removeChild(node: Node): void;
+    querySelectorAll<E extends Element = Element>(selectors: string): NodeListOf<E>;
 }
 
-type InjectableStyles = string | ElementStyles;
-type ElementStyleFactory = (styles: InjectableStyles[]) => ElementStyles;
+const styleLookup = new Map<string, ElementStyles>();
+
+export abstract class ElementStyles {
+    /** @internal */
+    public abstract readonly styles: ReadonlyArray<InjectableStyles>;
+
+    /** @internal */
+    public abstract readonly behaviors: ReadonlyArray<Behavior> | null = null;
+
+    /** @internal */
+    public abstract addStylesTo(target: StyleTarget): void;
+
+    /** @internal */
+    public abstract removeStylesFrom(target: StyleTarget): void;
+
+    public withBehaviors(...behaviors: Behavior[]): this {
+        (this.behaviors as any) =
+            this.behaviors === null ? behaviors : this.behaviors.concat(behaviors);
+
+        return this;
+    }
 
-function isElementStyles(object: any): object is ElementStyles {
-    return object.brand === elementStylesBrand;
+    public withKey(key: string): this {
+        styleLookup.set(key, this);
+        return this;
+    }
+
+    public static find(key: string): ElementStyles | null {
+        return styleLookup.get(key) || null;
+    }
 }
 
-function reduceStyles(styles: InjectableStyles[]): string[] {
+type InjectableStyles = string | ElementStyles;
+type ElementStyleFactory = (styles: ReadonlyArray<InjectableStyles>) => ElementStyles;
+
+function reduceStyles(styles: ReadonlyArray<InjectableStyles>): string[] {
     return styles
-        .map((x: InjectableStyles) => (isElementStyles(x) ? reduceStyles(x.styles) : [x]))
+        .map((x: InjectableStyles) =>
+            x instanceof ElementStyles ? reduceStyles(x.styles) : [x]
+        )
         .reduce((prev: string[], curr: string[]) => prev.concat(curr), []);
 }
 
-type HasAdoptedStyleSheets = ShadowRoot & {
-    adoptedStyleSheets: CSSStyleSheet[];
-};
+function reduceBehaviors(
+    styles: ReadonlyArray<InjectableStyles>
+): ReadonlyArray<Behavior> | null {
+    return styles
+        .map((x: InjectableStyles) => (x instanceof ElementStyles ? x.behaviors : null))
+        .reduce((prev: Behavior[] | null, curr: Behavior[] | null) => {
+            if (curr === null) {
+                return prev;
+            }
+
+            if (prev === null) {
+                prev = [];
+            }
+
+            return prev.concat(curr);
+        }, null as Behavior[] | null);
+}
 
-export class AdoptedStyleSheetsStyles implements ElementStyles {
-    public readonly brand: symbol = elementStylesBrand;
+// https://wicg.github.io/construct-stylesheets/
+// https://developers.google.com/web/updates/2019/02/constructable-stylesheets
+export class AdoptedStyleSheetsStyles extends ElementStyles {
     private readonly styleSheets: CSSStyleSheet[];
+    public readonly behaviors: ReadonlyArray<Behavior> | null = null;
 
     public constructor(
         public styles: InjectableStyles[],
         styleSheetCache: Map<string, CSSStyleSheet>
     ) {
+        super();
+        this.behaviors = reduceBehaviors(styles);
         this.styleSheets = reduceStyles(styles).map((x: string) => {
             let sheet = styleSheetCache.get(x);
 
@@ -43,31 +94,54 @@ export class AdoptedStyleSheetsStyles implements ElementStyles {
         });
     }
 
-    public applyTo(shadowRoot: HasAdoptedStyleSheets): void {
-        // https://wicg.github.io/construct-stylesheets/
-        // https://developers.google.com/web/updates/2019/02/constructable-stylesheets
-        shadowRoot.adoptedStyleSheets = [
-            ...shadowRoot.adoptedStyleSheets,
-            ...this.styleSheets,
-        ];
+    public addStylesTo(target: StyleTarget): void {
+        target.adoptedStyleSheets = [...target.adoptedStyleSheets!, ...this.styleSheets];
+    }
+
+    public removeStylesFrom(target: StyleTarget): void {
+        const sourceSheets = this.styleSheets;
+        target.adoptedStyleSheets = target.adoptedStyleSheets!.filter(
+            (x: CSSStyleSheet) => !sourceSheets.includes(x)
+        );
     }
 }
 
-export class StyleElementStyles implements ElementStyles {
-    public readonly brand: symbol = elementStylesBrand;
+let styleClassId = 0;
+
+function getNextStyleClass(): string {
+    return `fast-style-class-${++styleClassId}`;
+}
+
+export class StyleElementStyles extends ElementStyles {
+    public readonly behaviors: ReadonlyArray<Behavior> | null = null;
+
     private styleSheets: string[];
+    private styleClass: string;
 
     public constructor(public styles: InjectableStyles[]) {
+        super();
+        this.behaviors = reduceBehaviors(styles);
         this.styleSheets = reduceStyles(styles);
+        this.styleClass = getNextStyleClass();
     }
 
-    public applyTo(shadowRoot: ShadowRoot): void {
+    public addStylesTo(target: StyleTarget): void {
         const styleSheets = this.styleSheets;
+        const styleClass = this.styleClass;
 
         for (let i = styleSheets.length - 1; i > -1; --i) {
             const element = document.createElement("style");
             element.innerHTML = styleSheets[i];
-            shadowRoot.prepend(element);
+            element.className = styleClass;
+            target.prepend(element);
+        }
+    }
+
+    public removeStylesFrom(target: StyleTarget): void {
+        const styles = target.querySelectorAll(`.${this.styleClass}`);
+
+        for (const style of styles) {
+            target.removeChild(style);
         }
     }
 }
@@ -95,7 +169,12 @@ export function css(
         cssString += strings[i];
         const value = values[i];
 
-        if (isElementStyles(value)) {
+        if (value instanceof ElementStyles) {
+            if (cssString.trim() !== "") {
+                styles.push(cssString);
+                cssString = "";
+            }
+
             styles.push(value);
         } else {
             cssString += value;
@@ -103,7 +182,10 @@ export function css(
     }
 
     cssString += strings[strings.length - 1];
-    styles.push(cssString);
+
+    if (cssString.trim() !== "") {
+        styles.push(cssString);
+    }
 
     return createStyles(styles);
 }
diff --git a/packages/fast-element/src/view.ts b/packages/fast-element/src/view.ts
index 7d380e22bfb..0caaf5c5cd6 100644
--- a/packages/fast-element/src/view.ts
+++ b/packages/fast-element/src/view.ts
@@ -147,9 +147,10 @@ export class HTMLView implements ElementView, SyntheticView {
         parent.removeChild(end);
 
         const behaviors = this.behaviors;
+        const oldSource = this.source;
 
         for (let i = 0, ii = behaviors.length; i < ii; ++i) {
-            behaviors[i].unbind();
+            behaviors[i].unbind(oldSource);
         }
     }
 
@@ -158,16 +159,22 @@ export class HTMLView implements ElementView, SyntheticView {
      * @param source The binding source for the view's binding behaviors.
      */
     public bind(source: unknown): void {
+        const behaviors = this.behaviors;
+
         if (this.source === source) {
             return;
         } else if (this.source !== void 0) {
-            this.unbind();
-        }
-
-        const behaviors = this.behaviors;
+            const oldSource = this.source;
 
-        for (let i = 0, ii = behaviors.length; i < ii; ++i) {
-            behaviors[i].bind(source);
+            for (let i = 0, ii = behaviors.length; i < ii; ++i) {
+                const current = behaviors[i];
+                current.unbind(oldSource);
+                current.bind(source);
+            }
+        } else {
+            for (let i = 0, ii = behaviors.length; i < ii; ++i) {
+                behaviors[i].bind(source);
+            }
         }
     }
 
@@ -180,9 +187,10 @@ export class HTMLView implements ElementView, SyntheticView {
         }
 
         const behaviors = this.behaviors;
+        const oldSource = this.source;
 
         for (let i = 0, ii = behaviors.length; i < ii; ++i) {
-            behaviors[i].unbind();
+            behaviors[i].unbind(oldSource);
         }
 
         this.source = void 0;
@@ -202,10 +210,12 @@ export class HTMLView implements ElementView, SyntheticView {
         range.deleteContents();
 
         for (let i = 0, ii = views.length; i < ii; ++i) {
-            const behaviors = (views[i] as any).behaviors as Behavior[];
+            const view = views[i] as any;
+            const behaviors = view.behaviors as Behavior[];
+            const oldSource = view.source;
 
             for (let j = 0, jj = behaviors.length; j < jj; ++j) {
-                behaviors[j].unbind();
+                behaviors[j].unbind(oldSource);
             }
         }
     }