Many organisms use organic crystals for various functions, from light manipulation to nitrogen storage. These crystals are formed by specialized cells, in which remarkable control over the crystals is obtained using strategies beyond the state-of-the-art in man-made materials. While these cells were identified many years ago, almost nothing is known about their biology, particularly the cellular processes involved in organic crystal formation. We use biological tools together with physical and chemical methodologies to study these processes in zebrafish and medaka as our prima model organisms.