Two SVG smiley faces illustrate how React components can compartmentalize D3-generated geometry. The code builds a standard smiling face and a winking variant with a dimpled mouth, using D3's `arc()` and `line()` generators to create paths within reusable React components. Each facial feature—eyes, mouth, face circle—is its own component, demonstrating modular composition of SVG elements while keeping D3 and React separate concerns.