Melanosome transfer
Your tan is a delivery service. Melanocytes ship pigment to your skin cells like UV armor.
Grounded in the research on Melanosome (en.wikipedia.org/wiki/Melanosome)
Know what melanosomes actually are
Melanosomes are pigment-packed organelles built inside melanocytes, the dendritic cells sitting in your basal epidermis. They synthesize melanin (eumelanin = brown/black, pheomelanin = red/yellow) via tyrosinase, the rate-limiting enzyme. The melanocyte is the factory. It does not keep the pigment for itself.
Understand the transfer is the whole point
One melanocyte feeds roughly 30-40 keratinocytes through dendrite contact, the epidermal-melanin unit. Melanosomes ride to dendrite tips, get handed off, and stack into supranuclear caps over keratinocyte nuclei, literal UV umbrellas shielding your DNA. Your skin color is not how much pigment you make, it's how it gets distributed.