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Cover  We now take for granted that the basic components and mechanisms of all eukaryotic cells are conserved. However, only 20 years ago the relationship between animals and simple eukaryotes such as yeast was not so clear. One of the hallmarks of eukaryotes is a cytoskeleton, made up of actin filaments and microtubules. By 1984 it was known that yeast had genes for actin and tubulin, and that the yeast actin and tubulin proteins behaved in vitro like their animal counterparts, but little was known of the structure and function of the yeast cytoskeleton. Kilmartin and Adams (J. Cell Biol. [1984]. 98, 922-933) adapted fluorescence microscopy techniques to fixed yeast cells, revealing actin and microtubule structures that were quite simple in comparison to those in animal cells. Although simple, the yeast cytoskeleton was seen to change in characteristic ways during the well-defined cell cycle. The cover figure shows the stages of the cell cycle in cells of Saccharomyces uvarum (a close relative of the more common Saccharomyces cerevisiae) labeled with rhodamine-phalloidin (top) and anti-tubulin antibody. The numbers below indicate the percent of cells in a growing population showing the particular morphology. Filamentous actin is seen as cortical dots, generally associated with points of cell growth, and as fibers. Microtubules are seen as a bright intranuclear mitotic spindle that lengthens during the cycle and fainter cytoplasmic microtubules. This distribution of microtubules had been observed earlier in the pioneering electron microscopy experiments of Breck Byers and colleagues (Byers and Goetsch [1975]. J. Bacteriol. 124, 511-523). Soon after this work, conditional mutations were identified in the actin and tubulin genes (Shortle et al. [1984]. Proc Natl. Acad. Sci. USA. 81, 4889-4893; Thomas et al. [1985]. Genetics 111, 715-734), allowing a genetic analysis of the functions of the yeast cytoskeleton. This combination of genetics with morphological analysis has been particularly powerful, and the current challenge is to relate the wealth of information from the yeast genome sequence and associated genome-wide phenotypic assays with functional studies on the yeast cytoskeleton. The cover figure is reprinted from The Journal of Cell Biology, 1984, 111, p. 715-734 by copyright permission of The Rockefeller University Press.Tim Stearns