Novel photovoltaic perovskites, the organo-metallic lead halides (e.g. CH3NH3PbI3), have revolutionized the field of solar cells by their high photon to electron conversion efficiency η of 25%.  But due to their chemical and structural tunability (one can grow crystals from nanometer size to 1000 cm3), they offer to study a wealth of exciting physical phenomena and open further possibilities for applications. To illustrate them, a selected set of measurements will be reported together with some device prototypes.