Molecular biology has several distinct origins, but especially important are those contributed by fungal and yeast physiology, biochemistry and genetics. From the first gene action studies that became the basis of our understanding of the relationship between genes and proteins, through chromosome structure, mitochondrial genetics and membrane biogenesis, gene silencing and circadian clocks, studies with these organisms have yielded basic insight into these processes applicable to all eukaryotes. Examples are cited of pioneering studies with fungi that have stimulated new research in clinical medicine and agriculture; these studies include sexual interactions, cell stress responses, the cytoskeleton and pathogenesis. Studies with the yeasts and fungi have been effective in applying the techniques and insights gained from other types of experimental systems to research in fungal cell signalling, cell development and hyphal morphogenesis.