  The advent of the quantum gas microscope allowed for the in situ probing of
ultracold gaseous matter on an unprecedented level of spatial resolution. The
study of phenomena on ever smaller length scales as well as the probing of
three-dimensional systems is, however, fundamentally limited by the wavelength
of the imaging light, for all techniques based on linear optics. Here we report
on a high-resolution ion microscope as a versatile and powerful experimental
tool to investigate quantum gases. The instrument clearly resolves atoms in an
optical lattice with a spacing of $532\,\text{nm}$ over a field of view of 50
sites and offers an extremely large depth of field on the order of at least
$70\,\mu\text{m}$. With a simple model, we extract an upper limit for the
achievable resolution of approximately $200\,\text{nm}$ from our data. We
demonstrate a pulsed operation mode which in the future will enable 3D imaging
and allow for the study of ionic impurities and Rydberg physics.
