Since the early 1990s, when scientists first began using microarray devices to study gene expression, they9ve widened their horizons from focusing on brewer9s yeast to studying how genes are turned on and off in complex plants, pathogens, model animals such as the nematode and mouse, and human cancer cells. Some of these projects were on display last month at a meeting of microarray users organized by Nature Genetics in Scottsdale, Arizona.