  Type II superconductors, consisting of superconducting domains embedded in a
normal or insulating matrix, undergo a rounded phase transition. Indeed, the
correlation length cannot grow beyond the spatial extent of the domains.
Accordingly, the thermodynamic properties will exhibit a finite size effect. It
is shown that the specific heat and penetration depth data of a variety of type
II superconductors, including cuprates, exhibit the characteristic properties
of a finite size effect, arising from domains with nanoscale extent. The finite
size scaling analysis reveals essential features of the mechanism. Transition
temperature and superfluidity increase with reduced domain size. The combined
finite size and isotope effects uncover the relevance of local lattice
distortions
