Root/container discussion Source Name URL antd https://github.com/ant-design/ant-design/blob/master/components/button/button.tsx atlassian container https://bitbucket.org/atlassian/atlaskit-mk-2/src/master/packages/core/textfield/src/theme.ts auth0 https://github.com/auth0/styleguide/blob/master/packages/components/src/forms/index.styl bootstrap https://github.com/twbs/bootstrap/blob/master/scss/forms/_form-control.scss carbon https://github.com/carbon-design-system/carbon/blob/master/packages/components/src/components/text-input/_text-input.scss evergreen https://github.com/segmentio/evergreen/blob/master/src/text-input/src/TextInputField.js fabric root https://github.com/microsoft/fluentui/blob/master/packages/react-next/src/components/TextField/TextField.base.tsx stardust root https://github.com/microsoft/fluentui/blob/master/packages/fluentui/react-northstar/src/components/Input/Input.tsx fast https://github.com/microsoft/fast-dna/blob/master/packages/web-components/fast-foundation/src/text-field/text-field.template.ts lightning https://www.lightningdesignsystem.com/components/input/ materialComponentsWeb container (design) / root (code) https://material.io/components/text-fields#anatomy primer https://primer.style/css/components/forms semantic https://github.com/Semantic-Org/Semantic-UI/blob/master/dist/components/input.css spectrum https://github.com/adobe/spectrum-css/blob/master/components/textfield/index.css w3 n/a Most of the design systems / libraries do not have a generic name for the outer-most slot.