A smiling face drawn with D3.js animates by repeatedly moving its eyebrows up and down. The visualization demonstrates fundamental DOM manipulation by building the face from SVG shapes, including circles for the head and eyes, rectangles for the eyebrows, and a path generated with the `d3.arc` helper for the mouth. Using D3 v5 and the `select` API, the eyebrows are animated with chained `transition` calls, each lasting two seconds, to create a looping motion.