This heatmap visualizes user demographics by profession and gender, with color intensity representing income levels. Built with D3.js v7 and React, it uses SVG rendering to display the grid of colored cells. The visualization includes a sequential blue color scale for income values, a gradient legend, and interactive tooltips showing detailed demographic information. The data is loaded from an external CSV file using d3.csv, with d3.autoType parsing the data. Axes are rendered using d3.axisBottom and d3.axisLeft, while d3.scaleBand positions the categorical variables.