Micro Tetris
Jeroen writes "Students from the Vrije Universiteit Amsterdam used a so-called 'optical trap' to construct a version of Tetris that measures 25 x 20 micrometers. Blocks are constructed from tiny glass beads and all the action takes place in a waterdrop under a microscope. Considering the equipment needed, this must not only be the smallest, but also the most expensive Tetris clone around. A short description and a movie can be found here."
I bet you thought you were joking about the cancer thing, but check this out.
My deviantArt site