H2O – water – is a tasteless, odorless, colorless chemical substance, and the main component of Earth's rivers, lakes, oceans, and so on. Water is needed for almost all known life and makes up approximately 70% of the human body. It is a crucial participant in most functions critical to life, including breathing, digestion, and muscle movement.. It is a brilliant solvent, meaning that other substances can easily dissolve in it. This allows water to carry nutrients to cells, and carry waste out. Water also finds ample use in everyday life in such applications as cooking, bathing, and drinking.