The POLDER and Parasol instruments measure the directional and polarization signatures of the Earth reflectances. The primary use of these signatures is for aerosol monitoring. Indeed, polarization is a great tool to measure aerosols over land surfaces although the POLDER concept has some limitations that may be solved with the forthcoming APS instrument onboard the GLORY satellite. There are other use of the polarization, in particular for cloud phase, cloud drop size and ice plate orientations. The seminar will make a broad presentation of polarization signatures as they have been observed by POLDER and Parasol, and what use has been made of it.