Fluorescence image of a Caulobacter crescentus biofilm. Cells are labeled in red, holdfasts are labeled in blue, and extracellular DNA is labeled in green and shows up as yellow when superimposed with the red labeling of cells. The bright red area contains thousands of cells in a biofilm. Adjacent to the biofilm, individual cells can be resolved, in some cases attached to each other by eDNA-coated holdfasts (green)