GAIA will be of paramount importance to understand the Galactic structure. Here we focus on the determination of the star formation history (SFH) of the Galactic disk and bulge. We discuss whether GAIA will be able to isolate a sample of stars with the same characteristics of Hipparcos data (completeness over a certain critical magnitude and high precision in the distance) which will cast light on the SFH of the whole disk. We analyze the expected results in two directions, namely the BW and the Galactic pole. Finally we discuss the contribution of GAIA to the study of the SFH of the bulge.