Cell polarity plays an important role in nearly every aspect of biology, from polarized cell growth and asymmetric division in microbes to the organization of the human brain. Loss of cell polarity correlates with formation of cancerous cells. The goal of our lab is to understand how cell polarity arises in embryos of the nematodeCaenorhabditis elegans. PAR proteins, discovered in C. elegans, play a central role in polarization of many cell types in a wide variety of animals. Studies of these proteins have provided insight into polarity establishment in nematodes, flies, and mammals.