The single most abundant material in living matter is water. Living matter is mostly made up of hydrogen, oxygen, carbon and nitrogen. These four elements make up 96.5% of the atoms in all living things. Two hydrogen atoms and one oxygen atom bond together to make up water.
The exact amount of water contained in a living organism’s mass varies, but it can be up to 90%. A human adult body is made up of 60% water. The brain, organs and muscle contain 70 to 85% water, while the skin contains 60%. The bones are composed of 31%. Water is essential to human function as it aids every body system.