The Schaechter–Maaløe–Kjeldgaard papers, which have their 50th anniversary this year, have major implications for understanding the cell cycle, control of cell growth, control of cell size, metabolic control, the basic bacterial growth curve, and myriad other bacterial and eukaryotic growth phenomena. These ideas have broad applications that should be considered in current studies of the cell cycle. In particular, the emphasis on steady‐state growth conditions, and clear and sharp changes in growth conditions were fundamental to their experiments and have (...) been codified in the principles of the Copenhagen School of Microbiology. BioEssays 30:1019–1024, 2008. © 2008 Wiley Periodicals, Inc. (shrink)