Early plants were tiny algae and, like every other form of life, confined to water. To make it on the land they had to combat gravity, just like animals. They evolved a skeleton made up of rings of lignin which is the plant’s equivalent of bone. They could then leave water and stand alone. Lignin gave the plant cells strength to keep on growing up and up, reaching towards the sunlight. Lignin eventually expanded to fill up the cell walls and form wood. Wood allowed plants to evolve into trees, the incredible hulks of the land. Eventually the battle for light led to lush forests. These cool, shady and moist forests provided ideal conditions for delicate creatures like our ancestors.