This example demonstrates fundamental DOM manipulation with D3.js by building an animated smiley face out of SVG shapes. The code uses `d3.select` to append a circle for the head, two circles for eyes, rectangles for eyebrows, and an `d3.arc()` path for the mouth. D3 transitions animate the eyebrows upward and back over four seconds. The example uses D3 v5 and relies on simple attribute setters like `.attr()` to position each element.