This visualization shows a hierarchical tree of patient health records, where each node represents an individual with their age, blood pressure, and cholesterol levels. Node size encodes blood pressure, while color indicates cholesterol risk categories (green, amber, red). Built with D3.js v7, the code uses `d3.stratify()` to build the hierarchy, `d3.tree()` for layout, and `d3.linkHorizontal()` for curved links, rendering the final result as SVG circles and labels.