Specific and non-specific adhesion of bacteria to tissue were described. In today, non-specific absorption of bacteria and tissue will be well understood by DLVO-theory in colloidal chemistry. After the adhesion, glycocalyx was produced from the adhesive bacteria around their bodies, under the condition of a weak interaction with host cells. Each bacterium aggregate with approximate bacterium through glycocalyx and then bacterial biofilm is formed on the surface of tissue or surface of medical devices that is entered in living bodies. Bacterial biofilm has strong resistance for attack of antimicrobial agents, phagocytes and immunoglobulin. Clinical characteristic of biofilm diseases is intractable and infectious repeating, because the sessile bacteria are often released from bacterial biofilm and they often cause infection.