Number theory! Though arguably far removed from science, it provides such beautiful images that I couldn't resist. These two are produced from an extremely simple rule: fix a prime p, and set square (i, j) black if i*j reduced modulo p is greater than j, and white otherwise (the primes I used are 401 and 601). The lines going across halfway up, one third of the way up, etc. are easily explained, as are the hyperbolas around the corners. More mysterious—and visually striking—are the stars that form around the center and the different patterns that occur within them. Finally, along with the obvious vertical and horizontal symmetries, there is a hidden symmetry which I'll let you discover for yourself.