Bacteria have been long considered primitive organisms, with a lifestyle focused on the survival and propagation of single cells. However, in the past few decades it became obvious that bacteria can display sophisticated group behaviors. For instance, bacteria can communicate amongst themselves and with their hosts, by producing, sensing, and responding to chemical signals. By doing so, they can sense their surroundings and adapt as to increase their chances of survival and propagation. Here, we review the discovery of bacterial intercellular communication, some of the signaling molecules identified to date, the role of intercellular signaling in symbiotic and pathogenic relationships between bacteria and their hosts and its implications for the development of new therapeutic strategies against human disease.