Cell polarization is used both to mediate physical fates, as, for example, in orientated cell migration, and to specify differential phenotypic fates, as in the asymmetric division of stem cells. Strikingly, the same sets of conserved proteins are used throughout the Metazoa for these purposes. The PAR proteins organize cell polarization in many contexts, and the PINS proteins control the orientation of mitosis. These proteins seem to function as components of a self-organizing network, and an important goal is to decode — or parse — the molecular language of this network.