A biofilm is a large community of bacteria, algae, fungi or protozoa adhering to surfaces or interfaces. It forms preferably in aqueous systems, either on the water surface or on an interface to a solid phase. The complex accumulation consists of different species embedded in a layer of mucus. This film protects microorganisms in the human body, for example, from attacks by the immune system. Biofilms can cause diseases, for example, if they develop on teeth (caries), implants or catheters or settle in water pipes. Scientists are looking for ways to effectively dissolve biofilms to prevent serious infections.