Simple. What it is? And why is it special?

(This time, the order doesn’t matter much, so I can’t really mess up).

Went uncracked.

Answer

Most of you got the tetris part right, but that’s not what makes it special. This is, officially, the worlds smallest ever game of Tetris, being played by “optically trapping 42 glass microspheres (1 μm diameter) in a 25 μm x 20 μm sized field under a microscope. Their positions are then steered with a computer.“