In this talk I will discuss the
next frontier of research on the Cosmic Microwave Background (CMB): precisely
measuring the gravitational lensing of the CMB.
This CMB lensing signal encodes a wealth of statistical information
about the distribution of matter in the Universe, which is sensitive to the
total mass of the neutrinos, the nature of dark energy, and the particle
properties of dark matter. I will
discuss recent progress using data from ACTPol, and forecasts for the upcoming
AdvACT, Simons Observatory, and CMB-S4 experiments. I will also discuss a novel
and powerful way to probe dark matter particle properties using very high
resolution CMB lensing measurements, which can distinguish between cold dark
matter and alternative dark matter models that suppress small-scale structure.