This visualization shows more than 500 exoplanets discovered before October 2015 (about 1/4 of all exoplanets), sorted according to their temperature and density.
Various known classes of exoplanets are shown on the graph, for example, super-lands, hot Jupiter, hot Neptunes, water worlds, gas dwarfs or superdense diamond planets.
All visualizations are based on calculating the radius and temperature of the planet, but other factors, such as density, age or "stellar metallicity" have also been taken into account. These visualizations are very close to reality, but the true nature of the exoplanets depicted can be radically different.
Is not it an incredible variety of alien worlds?