This visualization displays the population and predominant religion of the world's 20 largest countries using horizontal stacked bars. The chart uses a color legend to allow interactive filtering, where hovering over a religion highlights the corresponding segments of each bar while dimming the rest. Built with React, the visualization leverages D3.js for data binding, scales, and layout, while employing the `d3.layout.stack` API to create the stacked bar structure and `d3-tip` for custom tooltips showing exact values. The data is formatted with a custom SI tick formatter that abbreviates billions as "B".