Cytomes are the cellular systems, subsystems, and functional components of the body. The cytome is the collection of the complex and dynamic cellular processes (structure and function) underlying physiological processes. It describes the structural and functional heterogeneity of the cellular diversity of an organism. The study of cytomes is called Cytomics.

The Human Cytome Project is about the study of the biological system structure and function of an organism at the cytome level. It relates to Cytomics, which is the study of cell systems (cytomes) at a single cell level. At the Focus on Microscopy (FOM) meeting in Philadelphia, on Wednesday afternoon, 7 April 2004, the idea of a Human Cytome Project was for the first time discussed at a scientific meeting.