Animal tissues and organs are formed by different types of cells that are arranged in stereotyped patterns. Although we know much about the mechanisms by which cells acquire different fates, we know very little about how cells interact to arrange themselves to form these patterns. We are suggesting a project that investigates cell affinity, an important but neglected aspect of cell behaviour that is especially relevant to understanding development. We would like to host a PhD student to work on a project that is related to but not overlapping too closely with our own main project on planar cell polarity. Anyone interested should please read a bit about us (making-of-fly.me), a review on affinity (R. A. Foty, and M. S. Steinberg. Wiley Interdisciplinary Reviews: Developmental Biology 2013 2: 631-645) and also the paper we have written specifically on cell affinity (P.A. Lawrence, J. Casal, G. Struhl. Development 1999 126: 2441-2449). Our experiments suggest a good way into this area using both genetics and genetic mosaics. We can provide research costs and a student salary (including university fees and maintenance) from our Wellcome Trust grant.