Chlorophytes range from tiny unicells, just big enough to see with the light microscope (one is even the smallest eukaryote known), to some quite large forms over a metre across. They include the largest known cells, a green alga called Ventricaria ventricosa that is one cell that may be several centimetres in diameter. It occurs on coral reefs, where the cell wall is often overgrown by thin, pink coralline red algae. It is able to grow to a large size and retain a rigorous shape purely because of turgor pressure. Any tiny hole in the cell, and it collapses like a wet balloon.