The regular appearance and the repetitive nature of theDrosophilaeye, consisting of several hundred identical multicellular units, the ommatidia, has long served as an invaluable experimental system to study cell-cell interactions, inductive signaling events, cell proliferation, programmed cell death, cell differentiation, cell organization, and planar cell polarity among others. Importantly, the eye is dispensable for viability and fertility of the fly and thus, it can easily be manipulated, making it an ideal target for genetic screens. This chapter described an essential technique in the analysis of different genotypes in the adult fly eye, and allows detailed analyses with single cell resolution.
