Melanosome

They have a characteristic ultrastructure on electron microscopy, which varies according to the maturity of the melanosome, and for research purposes a numeric staging system is sometimes used.

Cytoplasmic dynein will carry the vesicles containing the melanin to the center of the cell, which causes melanosomes to sequester the keratinocyte's nucleus, providing optimal protection from UV rays.

[citation needed] In many species of fish, amphibians, crustaceans, and reptiles, melanosomes can be highly mobile within the cell in response to hormonal (or sometimes neural) control, which leads to visible changes in colour that are used for behavioural signaling or photoprotection.

The motor protein dynein is responsible for concentrating the melanosomes toward the center of the cell, or the "minus end" of microtubules.

Conversely, the protein kinesin is responsible for dispersing the melanosomes to the periphery of the cell, and are plus end directed motors.

[5][6] Recent (2008) discoveries by Xu Xing, a Chinese paleontologist, include fossilized feathers in rock formations dating from the Jurassic period (200 to 150 million years ago) to the late Paleogene and Neogene periods (66 to 2 million years ago).

It is conjectured that these microscopic structures could be further studied to reveal the original colors and textures of softer tissues in fossils.