A smiley face built with D3.js demonstrates basic DOM manipulation and animation. The face is drawn using SVG shapes, including a yellow circle, two eyes, and a mouth created with the `d3.arc` shape generator. The code uses `select`, `append`, and `attr` to construct the scene. An animated sequence, driven by `transition().duration()`, moves the rectangular eyebrows up and down in a repeating loop, showcasing D3's ability to tween attributes over time.