This D3.js bubble chart visualizes the correlation between GDP per capita, life expectancy, and population for 25 countries. The x-axis represents GDP in USD, the y-axis shows life expectancy in years, while bubble size encodes population in millions, and color distinguishes each country. The visualization uses `d3.scaleLinear` for axes and bubble size, `d3.scaleOrdinal` for color assignment, and `d3.axisBottom` and `d3.axisLeft` for tick marks. Interactive tooltips appear on mouseover, displaying detailed country data, implemented with SVG `circle` elements and HTML div overlays. A legend with sample circles and labels explains the population scale.