Elastin structures and their significance towards elastic recoil properties have been reviewed. Starting from the initial hypothesis that elastin conformation is conditioned by that of its monomer, the structure of tropoelastin was first described using theoretical and experimental methods and a beta class folding type was evidenced for the isolated unbound tropoelastin molecules. The structure of elastin in the solid state was consistent with that of its monomer and consequently, fibrous elastin appeared constituted of globular tropoelastin molecules. Finally, theoretical and experimental considerations have led us to the conclusion that the functional form of the elastomer, water swollen elastin, could be a triphasic system comprising the protein chains, hydration water and solvent water. Following this description, the dynamic structural equilibria occurring within elastin hydrophobic domains and the plasticizing effect of water could explain elastin elasticity, in keeping with a classical entropic mechanism.