Microlensing is uniquely capable of studying planets across a wide range of masses at a few AU from their host stars. At the lower masses, these planets are difficult to impossible to find with other techniques. I will discuss recent results in microlensing suggesting a turnover in the planet mass ratio function around 10^-4, i.e. that planets with mass ratios similar to Neptune are the most abundant at separations probed by microlensing. I will also discuss how current and future microlensing surveys, including WFIRST, will advance our understanding of cool planet populations.