The paper reports on the single-atom and single-site resolved fluorescence imaging of strongly interacting bosonic Mott insulators in an optical lattice. The authors achieve high-resolution imaging, allowing them to fully reconstruct the atom distribution on the lattice and identify individual excitations with high fidelity. By comparing radial density and variance distributions with theoretical models, they measure the in-situ temperature and entropy of the system from single images. They observe Mott-insulating plateaus with near-zero entropy and resolve high-entropy rings separating them, despite their width being only a single lattice site. The study also demonstrates how a Mott insulator melts as the temperature increases due to the proliferation of local defects. This work opens new avenues for the manipulation and analysis of strongly interacting quantum gases on a lattice, as well as for quantum information processing with ultracold atoms. The high spatial resolution enables direct addressing of individual lattice sites, which is crucial for implementing novel cooling schemes for atoms on a lattice.The paper reports on the single-atom and single-site resolved fluorescence imaging of strongly interacting bosonic Mott insulators in an optical lattice. The authors achieve high-resolution imaging, allowing them to fully reconstruct the atom distribution on the lattice and identify individual excitations with high fidelity. By comparing radial density and variance distributions with theoretical models, they measure the in-situ temperature and entropy of the system from single images. They observe Mott-insulating plateaus with near-zero entropy and resolve high-entropy rings separating them, despite their width being only a single lattice site. The study also demonstrates how a Mott insulator melts as the temperature increases due to the proliferation of local defects. This work opens new avenues for the manipulation and analysis of strongly interacting quantum gases on a lattice, as well as for quantum information processing with ultracold atoms. The high spatial resolution enables direct addressing of individual lattice sites, which is crucial for implementing novel cooling schemes for atoms on a lattice.