Details in retopology I'm doing a retopology of a skull. In some areas, the model appears through the retopology mesh. For this reason, i think i'm making too many faces, so it fits perfectly. Am I doing right? Also, I've read something about baking, and i don't know if it's only for texture. 

So, for example: what should i do in that incision?

Notes: subsurf and shrinwrap mods are on
You could continue to retopologize over this incision. 
When your retopology is over, you would UV unwrap it, and do some displacement map baking, or normal map baking. 

Then you can use the baked displacement (or normal map) textures on your retopologized model. So the incision would not be in the topology, but in the texture (normal map, or displacement). So it would be visible in your render.