This example displays a choropleth map of Swedish counties (laen) using geographic data from a TopoJSON source. The visualization renders province boundaries as filled shapes in a blue-teal color, with interior borders highlighted in green, all drawn through SVG paths generated by `d3.geoPath` and the `geoMercator` projection. Built with React and d3.v5, the code applies the projection’s `fitExtent` method to scale and position the map within the viewport. The map is populated using `topojson.feature` and `topojson.mesh` to extract geometries and internal boundaries from the fetched dataset.