There are typefaces that attempt to remain legible at ludicrously small sizes. Ken Perlin's Tinyfont attempts to do so while retaining traditional letterforms, putting LCD subpixels to clever use. There are various 3x5 pixel fonts for those who prefer the crisp purity of the traditional pixel, and prior attempts at the holy grail of a legible 3x3 nerd font.
Minima is an effort to make the perfect 4x4 pixel font, allowing itself a little more space but also going step further toward abstraction, abandoning legibility in favor of more easily-distinguished characters. It's €10 and I need a tylenol.