Tree Map Charts are predominantly used in cases of hierarchical data representation. The points of this chart type look like rectangles of different width and height and colored in a hue of a Color Scale according to the value the point represent.
Here you can see a TreeMap Chart where the points (or cells) of the root level are representing the population in the states of the USA and the points of the lower level shows the population in towns. On both levels, the labels show the name of the state (town) and the whole population value. Color Scale uses the colors from red to light orange for the values from the highest to the lowest. The mostly populated state is California with 18 383 442 people, the most populated town in California is Los Angeles with 3 792 621 people. The less populated state and its town are Montana with 104 170 people and its only described town (Billings).