Receiving information from the environment, as well as sending information to another cell is an inevitable process in the living world. Multicellular organisms have a complex task to coordinate and control signal transmission among neighbouring cells in order to maintain homeostasis. Integrins are important molecules which are involved in bidirectional signaling, from the environment to the cell and vice-versa. Integrins are heterodimer transmembrane receptors restricted to multicellular organisms. They are composed of a globular extracellular head domain, leg domain and short cytoplasmic domain. Integrins reside in three alosteric conformations: inactive bent conformation, intermediate and active extended conformation. Ligand binding to integrin head domain induces conformational change which is transmitted along the molecule to the cytoplasmic domain. It is also possible to activate the ligand binding site on the integrin head by efector binding to cytoplasmic tail. This kind of signal transfer is bidirectional. As they are generally adhesion receptors binding to proteins of extracelular matrix (ECM), main integrin function is cellular adhesion. Additionally, they participate in cytoskeleton binding and remodelling, thereby in cell migration. As metastasis is dependent on cellular anchorage it is evident that integrins play an important role in cancer cell invasion. Integrins are significant for apoptosis induction and help in cell survival. Furthermore, they are important for cell proliferation, lymphocyte binding to endotel cells and antigen recognition. Obviously, integrins are important molecules included in many cellular processes. They are „sensors“ which monitor events in the environment and transmit signals to direct cellular behavior.