A smiling face is drawn with D3.js, rendered as SVG shapes and animated with the transition API. The code uses D3 v5 to construct a yellow circle head with eyes and a path-based mouth, generated via the `arc` function with specified inner and outer radii. Eyebrows move up and down over two seconds using chained `transition` calls, showcasing animation of SVG attributes. The example relies on D3's `select` and `append` for DOM manipulation, with geometry defined by variables for spacing and offsets.