Algae colonies, such as the Volvox one shown here, are propelled through water by the coordinated movements of their whip-like flagella. Now a team of scientists from the University of Arizona and Brown University has found that the beating flagella also concentrate vital nutrients in front of the swimming colony. Biologists had not previously understood how a group of single-celled organisms could get the extra fuel needed to multiply and create colonies, which can include up to 50,000 individuals. This new finding shows how the algae are able to feed, explaining a critical step in the evolution from single-cell to multi-celled organisms. Above, illuminated plastic beads show the current flow created around the Volvox colony. The research is detailed in the early online edition of the Proceedings of the National Academy of Sciences.