  A particular strength of ultracold quantum gases are the versatile detection
methods available. Since they are based on atom-light interactions, the whole
quantum optics toolbox can be used to tailor the detection process to the
specific scientific question to be explored in the experiment. Common methods
include time-of-flight measurements to access the momentum distribution of the
gas, the use of cavities to monitor global properties of the quantum gas with
minimal disturbance and phase-contrast or high-intensity absorption imaging to
obtain local real space information in high-density settings. Even the ultimate
limit of detecting each and every atom locally has been realized in
two-dimensions using so-called quantum gas microscopes. In fact, these
microscopes not only revolutionized the detection, but also the control of
lattice gases. Here we provide a short overview of this technique, highlighting
new observables as well as key experiments that have been enabled by quantum
gas microscopy.
