Fimbriae are thin, hair-like structures found on the surface of many 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. These structures are different from flagella, which are used for movement. Fimbriae can vary in number and length among different bacterial species, influencing their ability to form biofilms and contribute to pathogenicity. Understanding fimbriae is essential in microbiology and can aid in developing treatments for bacterial infections.