Biofilms are physical groups of microorganisms growing together on a surface. The metabolic activities of members of the biofilm cause the environment to be heterogeneous, and bacteria in different regions of the group have different capabilities. As a consequence of growth in a biofilm, any individuals in the group can tolerate high levels of antibiotics. For this reason biofilm infections are very difficult to treat. The molecular basis of the antibiotic tolerance is controversial. We have been engaged in understanding a better view of the biology of biofilms to inform us about how to design more effective therapies and we have been developing potential new therapies.