Building React components that are aware of their size and position on the screen can enhance their functionality, especially for responsive layouts, canvas redraws, and components that change based on size constraints. Libraries like react-measure and react-sizeme address these needs by enabling components to react to their size changes. React-measure wraps a component and calls an onResize function when changes occur, although it struggles with unknown initial dimensions. React-sizeme tackles this initial measurement issue by performing a lightweight, invisible render to determine size, allowing components to render correctly from the start. While react-sizeme is beneficial for initial rendering based on dimensions, it introduces a slight performance overhead, making react-measure more suitable for components that mount frequently. Both libraries have minor latency in detecting size changes, which can affect perceived performance slightly, but they provide effective solutions for creating size-aware components in React.