Bacterial adhesion to intraocular lenses (IOLs) takes place during their implantation. This is a prominent etiological factor of postoperative endophthalmitis. Following adhesion, secretion of an extracellular matrix (called slime for Staphylococcus epidermidis) and formation of multiple layers of microcolonies lead to the colonization of the biomaterial surface. Scanning electron microscopy photographs illustrate the different steps of biofilm formation. The different adhesins expressed by S. epidermidis involved in the adhesion process are described. The biofilm is not only an adhesive medium; it also affects virulence. Last, notions on biofilm physiology are discussed in an attempt to explain the dynamic equilibrium of this system. In 2004, the perfect biomaterial able to prevent postoperative endophthalmitis does not yet exist. Moreover, there is no effective tool, at the present time, to fight against mature biofilms. Therefore, preventing biofilm formation remains capital, which requires perfect knowledge of all stages of formation and the factors involved.