Congratulations to A. Hyun (Annie) Kim, Ben Krummenacher, and Jason Yeung on this new publication, available online at this link. In this study, we followed individual receptor signaling complexes as they assembled and disassembled in real time, comparing cellular responses to IL-1 cytokine orthologues separated by over 100 million years of evolution. Despite large differences in ligand–receptor affinity across species, each signaling complex produced a discrete, quantized packet of signaling flux rather than a graded output—revealing a conserved unit of information transfer within the pathway.