A stacked bar chart shows Sales across Product Sub-Categories, with bars segmented by Customer Segment, using a categorical color scale. The visualization renders as SVG via D3 v3’s `d3.layout.stack`, `d3.scale.ordinal`, and `d3.svg.axis`, with a legend from d3-legend. Data is loaded from a CSV file containing order details, while axes use a custom SI tick formatter that converts billions to "B".