One of the main goals of Planck is to measure the Cosmic Microwave Background (CMB) polarization better than before. Planck has provided the sharpest, cleanest view of the Cosmic Microwave Background radiation. In the future, it will provide measurements of the polarization across the sky better than before. Planck does this by measuring the E-mode polarization with uncertainties small enough to recover harmonic content, and to detect the B-mode polarization. The polarization measurements will be used to address the reionization history of the universe and the existence of tensor mode perturbations due to gravitational waves in the very early universe.