Water is key to life, with living things being largely composed of water, and reliant on water either as a living substrate, a primary intake need, or subtle combinations of these. Aquatic animals live in water, terrestrial animals need to drink water, or at least eat food with sufficient water content for their needs. Plants need water like animals do, for maintenance of cells and intercellular integration. They also need it for photosynthesis, the living solar energy capture that drives so much of the ecosystem processes that support life on earth. Microbial life also uses water as its substrate for living, growth and movement. Microbial lifeforms generally have a very high water content when active.