This visualization maps CAR-T therapy targets across cancer types using a bubble chart. It groups targets like CD19 and CD30 into hierarchical circles representing hematologic malignancies and solid tumors. The code uses d3.pack and d3.hierarchy to position circular nodes, with d3.scaleOrdinal and d3.schemeBlues coloring them by depth. Data comes from a local JSON file, rendered as SVG using d3.json and appended circles and text labels.