Rock

Okay, not rock at all.

But it is the rock upon which we build our conscious lives.

Not a human brain but that of what are sometimes called "Death's Head" monkeys due to its face which I am sure peering out of the trees in the dark could be quite alarming. Squirrel monkeys are the more palatable name.

This particular brain has been very carefully sliced, stained, and mounted between two very thing pieces of glass. This is a negative shot of the result.

Oh, by the way, this slide (not the photo) is a good 40 years old and is mounted among several others on the wall of my study. Just thought it might be a different blip for such a grey day.