Grass

Grass is a natural block which can be found naturally in the world. It cannot be legitimately obtained; instead it must be grown in the world.

Generation
Grass is generated as a topsoil layer when a new world is created. It often comprises the top layers of terrain, followed by several layers of Dirt underneath.

Behaviour
Grass has the ability to randomly spread to Dirt blocks within 2 blocks horizontally and 1 block vertically. Grass spreads slowly, and will not spread to dirt blocks that are not in sunlight.

Grass will also turn to Dirt if the block above it is opaque. This means Grass cannot spread underwater, but will not revert to Dirt underwater.