Until now, the only way to isolate graphene is to cleave Graphite on top of an oxidized Si wafer and then carefully scan its surface in an optical microscope. Thin flakes are sufficiently transparent to add to an optical path, which changes their interference color with respect to an empty wafer. Contrast spectra and contrast images on SiO2 or Si3N4 or PMMA films can be used to determine the number and optical properties of graphene layers.