This example presents a minimal starting point for building React + D3 visualizations. It shows a blank SVG canvas with distinct gray outer and inner rectangles, visually exposing the chart's margins and plot area boundaries. The code uses React's component model and D3 v6, loaded via CDN, with a `VizContainer` component that abstracts SVG and group elements. The `showMargins` prop controls whether the margin rectangles render, and the main `App` component defines the canvas dimensions and margin constants.