Density is enormous, between one and ten million grams per cubic centimeter. This is tons per cubic centimeter. White Dwarfs have no source of energy, so they will gradually cool. Because their pressure has nothing to do with temperature, their radius remains constant. Star moves steadily down and to the right.
Exact track depends on mass.
After an eternity, these stars will cool so dim they will become invisible. This is the final stage in their life. Eventually, elements beyond Helium can start burning. Star doesn't move on H-R diagram. Core of star is Iron.