A smiling face rendered in SVG uses D3.js v5 to demonstrate fundamental DOM manipulation and animation. The code draws a yellow circle with eyes, cheeks, pupils, eyebrows, and a mouth using `d3.select`, `d3.append`, and `d3.arc`. Transitions animate the pupils shifting side-to-side and the eyebrows moving up and down via `transition.attr`. The example relies on D3’s selection and transition APIs to update SVG attributes, with no external data source.