The physical body is made up of countless numbers of tiny material particles called molecules and atoms. These material particles are constantly being replaced by material particles from the outside environment (in the form of food, water, air, and so on). Over a period of five to seven years, this process of metabolism brings about a complete change of the matter that makes up your body.

~ Chris Butler (Jagad Guru Siddhaswarupananda Paramahamsa)
Science of Identity Foundation