  High-performance instruments at large ground-based telescopes have made
integral field spectroscopy (IFS) a powerful tool for the study of extended
objects such as galaxies, nebulae, or even larger survey fields on the sky.
Here we discuss the capabilities of IFS for the study of resolved stellar
populations, using the new method of PSF-fitting crowded field IFS, analogous
to the well-established technique of crowded field photometry with image
sensors. We review early pioneering work with first generation integral field
spectrographs, the breakthrough achieved with the MUSE instrument at the ESO
Very Large Telescope, the remarkable progress accomplished with MUSE in the
study of globular clusters, and first results on nearby galaxies. We discuss
the synergy of integral field spectrographs at 8-10m class telescopes with
future facilities such as the Extremely Large Telescope (ELT).
