Area B aims at characterizing quantum cooperative dynamics of the collective degrees of freedom in mesoscopic systems. The aim is to push the limits of quantum cooperativity to the mesoscopic scale. The five projects conforming this area utilize different collective excitations across a wide range of different parameters. They include the dynamics of optomechanical collective modes of cold atomic ensembles, the properties of transport in crystals of trapped ions and in the presence of quantum defects, the controlled interaction of light with mechanical or magnetic degrees of freedom in nanostructured and levitated solid state systems.