Underlying the wonderful diversity of natural forms is the ability of an organism to grow into its appropriate shape. Regulation ensures that cells grow, divide and differentiate so that the organism and its constitutive parts are properly proportioned and of suitable size. Although the size-control mechanism active in an individual cell is of fundamental importance to this process, it is difficult to isolate and study in complex multi-cellular systems and remains poorly understood. It is therefore of interest to study size control in unicellular organisms, which are governed by simpler physiology: proliferate rapidly whenever environmental conditions permit. Therefore, the Skotheim laboratory studies size control in budding yeast, a genetically tractable eukaryotic organism. Previous studies of the budding yeast cell cycle, which couples growth and division, have revealed mechanisms shared by both yeasts and humans. This leads them to believe their findings will be of general interest, particularly since mammalian size control genes are frequently mutated in cancers.