Reaching Critical Thresholds in Cosmology with CMB-S4

The cosmic microwave background (CMB) offers an unparalleled opportunity to advance our understanding of the fundamental physics of the universe. The CMB carries information about the earliest moments in the universe that could constrain inflationary models and quantum gravity. It also acts as a backlight to the formation of structure in the universe, giving us information about dark energy, dark matter, neutrinos, and particles beyond the standard model. With ~500,000 polarization-sensitive detectors, CMB-S4 will measure the CMB with unprecedented sensitivity and reach critical thresholds in these areas of discovery. Observations with CMB-S4 will also open a new observational window of the time-varying millimeter sky. I will give an overview of the science achievable with CMB-S4 and the latest project status.