Array analysis of dividing cells has been tackled for yeast, but in the January Nature Genetics Cho et al. present the first large-scale analysis in human cells (Nat Genet 2001, 27:48-54). They identify 731 of 40,000 human genes and expressed sequence tags (ESTs) as being cell cycle regulated in primary fibroblasts, and use a functional classification system to identify coordinate regulation of pathways. Notable surprises include upregulation of motility-related genes in G₂ (perhaps to prepare daughter cells for migration away from each other), and of extracellular matrix-associated genes in M (possibly to enhance the re-establishment of cell-cell contact and communication after mitosis).