Biofilms are a widely observed growth mode in which microbial communities are spatially structured and embedded in a polymeric extracellular matrix. Here, we focus on the model bacterium and summarize the current understanding of biofilm formation, including initial attachment, matrix components, community dynamics, social interactions, molecular regulation, and dispersal. The regulatory network that orchestrates the decision to form and disperse from biofilms coordinates various environmental inputs. These cues are integrated by several transcription factors, regulatory RNAs, and second-messenger molecules, including bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP). Through complex mechanisms, weighs the energetic cost of forming biofilms against the benefits of protection and social interaction that biofilms provide.