Since 1998 the Earthshine Project has been a collaborative effort between Big Bear Solar Observatory/New Jersey Institute of Technology and the California Institute of Technology. Cyclic spectroscopic observations of the dark and bright sides of the moon (or earthshine and moonshine respectively) have been carried out in the visible range at Palomar Observatory. The ratio of the earthshine to moonshine spectra characterizes the globally averaged Earth's spectrum. These observations allow us to study global averaged column densities for several trace and non-trace atmospheric components. Revelant information concerning to the search of extra-solar, terrestrial-like planets can be also obtained from these observations.