Geneticists and biochemists both tend to represent signalling pathways as diagrams where abstract arrows connect molecular components. Yet signalling doesn’t occur in abstract space but within and between cells, so the cell biology of they systems needs to be considered. Our work on the interface of signalling and cell biology started with Drosophila genetics but is increasingly focused on the cell biology of proteins of the rhomboid-like superfamily. We are currently particularly studying the control of inflammatory and growth factor signalling in mammals.