Abstract: SrTiO3 is a semiconductor which, when doped with a low density of electrons, becomes superconducting with a dome-shaped doping dependence of the superconducting transition temperature. I will present optical, transport and specific heat data, and discuss a unified approach to the transport properties and superconductivity, showing that superconductivity emerges out of a liquid of interacting polarons. This interaction is rather weak, disfavouring the picture of uncondensed bipolarons above Tc.