Over the last decade, the concept of sessile microorganisms possessing a distinct developmental microbial lifestyle has been fully embraced in the disciplines of both microbiology and ecology. Cells adhere to each other at an interface aided by extracellular polymeric substances and develop into assemblages of microcolonies with more or less confluous architecture referred to as biofilms. While embedded in a biofilm, a cell’s phenotypic expression can be altered to a state not commonly found in planktonic cells (Costerton et al. 1995; Prigent-Combaret et al. 1999; Watnick and Kolter 2000). Claude ZoBell’s (1943) classic paper exemplifies the infancy stages of biofilm research by focusing on the effect of solid surfaces on microbial activity. ZoBell investigated marine environments, but biofilms are also routinely encountered in other environments, such as the rhizosphere. In this chapter, we begin with a historical account of biofilm research, summarize the current state of knowledge about biofilm formation processes, and discuss the prevalence of biofilms in soil and their role in agricultural systems.