One of the most fascinating life style of bacteria is the biofilm. Discovered in the last century, we are still learning on the molecular bases that lead the transition from planktonic to sessile life style characteristic of biofilms, and the way bacterial cells build their own “cities”. The assembly of the biofilm is complex and highly regulated involving a myriad of bacterial factors even multiple microbes, therefore, this process is included in a more global concept, the bacterial multicellularity and social behavior. In this research line, we are interested in the study of functional amyloids, the last addition to the group of structural factors that permit the construction of extracellular matrix of biofilms. Our research moves from basic and structural aspect to functional roles of amyloids in the bacterial physiology and interaction with other microbes or interkingdom communication.