Melanotan is a peptide that invigorates the natural secretion of melanin. This peptide is made and circulated inside the skin and when exposed to UV Rays makes the skin to get darker. Melanotan1 and 2 is an engineered analogue of this peptide which is designed to darken and tan the skin.
Melanin is a naturally secreted hormone which regulates the pigment in our skin. Put simply, the more the melanin in the body, the darker the pigment and subsequently the darker also the skin colour becomes.