From today's Daily Illuminator on the SJ Games site: the world's smallest dice (scroll down for more photos). Made of brass, for ony $870 you can have one of your very own.

They look like they're roughly 0.022 - 0.025mm on a side. That gives a diagonal of 330µm. For some accidental perspective, that would be a smidge more than the diameter of two optical fibers side-by-side. The pips look to be ~50µm; the width of the light transmitting core of a strand of multimode (short-haul) fiber.