An animated smiley face demonstrates fundamental DOM manipulation with D3.js. The face, rendered as SVG, features yellow circular head, eyes, and eyebrows that transition vertically in a looping sequence using chained `transition` calls. A mouth is drawn with `d3.arc` path generator. The code imports `select` and `arc` from D3 v5, using selections to append and style SVG elements while `transition().duration()` animates the eyebrow group’s transform attribute.