Fimbriae are thin, hair-like structures found on the surface of certain bacteria. They are primarily composed of proteins and play a crucial role in helping bacteria adhere to surfaces, including host tissues. This adhesion is important for colonization and infection, allowing bacteria to establish themselves in various environments. In addition to their role in adhesion, fimbriae can also facilitate the formation of biofilms, which are communities of microorganisms that stick to surfaces. Biofilms can be found in natural environments, as well as on medical devices, and can contribute to persistent infections. Understanding fimbriae is essential in microbiology and medicine.