Cyclotron Radiation Emission Spectroscopy is a new approach to measuring electron energies being actively developed by the Project 8 collaboration. The technique determines the energy of individual electrons by observing the changes in their cyclotron frequency resulting from their relativistic mass shifts. Our first demonstration of the methodology was made in 2014 and we have been working since then to evaluate and enhance the performance. Here I will review the principles of CRES and the experimental milestones achieved thus far. I will also briefly discuss progress towards using CRES for nuclear physics applications and specifically direct neutrino mass measurement in Project 8.