The Notch and Epidermal Growth Factor Receptor (EGFR) pathways regulate cell fate in the developing compound eye. These two pathways are used repeatedly to achieve different outputs. We find that a combinatorial model involving these two pathways is at the core of a subset of the cell-specification process. Our past work has suggested that these two pathways combine in parallel with their inputs integrated at the enhancer regions of target genes. More recent results suggest that these two pathways can also combine in series such that the EGRF pathway is responsible for the activation of the ligand for Notch. It seems clear that specific cell types do not arise from many different cell-specific signals, but rather from the proper spatial and temporal combination of a small number of signals acting on ubiquitously expressed transcription factors.