Hello, I don’t know how to say it in english so I’ll try, I saw somewhere I perfect head modeling and rigging and something impressed me: the eyes were not really round like real eyes and the eyelid “followed” the crystalline bumps. If is not clear imagine a mouse under a cover, you could follow its movements with the bump made by its body with the difference than this should be done with clothes in blender.
How to achieve this ? Is it simulated with shape key or is it possible for a bone to influence other bone by its physic position ?
Thanks in advance
Probably a Shrinkwrap modifier was used with a Vertex Group active. To do this add a vertex group to the head mesh, assign the eyelids to this group. Add a Shrinkwrap Modifier to the head with the eye meshes as the target and select your eyelids vertex group. Then when you rotate the eyes the vertex group vertices will stay on the eye mesh. 
Cheers, Clock.
Very simple in fact, I made a small test and it seems very good, thank you for you mini tutorial !