The Sun should be at the peak of its activity cycle, but actually it has been rather feeble. Several solar space observatories have been watching the Sun over the past few years: SoHO, Stereo, Hinode, SDO and IRIS . We now have high spatial and spectral resolution images of the Sun, with a high cadence. This talk will review what we have learnt about the active Sun, in particular what we know (and don’t yet know!) about solar active regions and flares, and how they might affect the Earth’s environment (via space weather).