Collagen is a protein substance contained in all human and animal connective tissue. The word "kolla" is originally from the Greek word "glue". It is collagen that holds everything together and forms the main component of all body tissue - connective tissue.

Collagen occurs in many parts of the body and makes up more than 30% of the protein mass in the human organism. So far, scientists have only identified approximately 29 sub-types of collagen. In the human body, over 90% of the collagen is Type I (CI), which is skin, bone, organs, tendons, vascular and ligature.

And from a molecular perspective, "Tropocollagen" i.e. the collagen molecule, is a long fibrous protein and not globular like other proteins. It is assembled into bundles of collagen fibrils known as collagen fibres.