With quantum gas microscopy we are now able to take the control of ultracold quantum gases in an optical lattice to the next and ultimate level of high fidelity addressing, manipulation and readout of single particles. In my talk I will first give an introduction to this field of research and present an overview of recent experiments. I will then focus on experiments in which we are for the first time able to directly measure entanglement entropy in a quantum many-body system, and use such measurements to explore quantum thermalization. These experiments shed light onto the amazing role of entanglement in quantum statistical mechanics. * Please note the new colloquium start time of 4 p.m.*