Macro on Monday - Guess What

Unfortunately no virtual Midmarsh Stars this week as everyone was stumped by last week's close shot of a roll of electrical insulation tape:

   

Maybe you will have better luck with the new mystery photo which is a cropped slice:
Guess What:


Please leave any guesses in the comments.
They will be revealed, along with the answer, next Monday.
No prizes, just for fun and maybe a virtual Midmarsh Gold or Silver Star.

Running even later than usual tonight. Spent hours trying to find out why I was seeing various spurious 'shapes' from the video cameras I have been trying on the microscope. At first I thought is was some dirt somewhere in the optics associated with the bottom lighting system. I cleaned everything up as best I could but it made no difference. They only show at high magnification but it wasn't the objective lenses. In the end I came to the conclusion it was some aberration in the cameras at the low lighting levels caused by the tiny openings used on high magnification lenses.

Also I am a woodpecker typist - only using two fingers on each hand. Unfortunately I managed to stab the end of one finger on my freezer knife which has two saw like edges. So one hand has to be careful not to put pressure on that finger as it starts bleeding again and that is slowing things down somewhat.