Electrons within galaxy groups and clusters Thomson scatter CMB photons out of and into the line of sight, an effect known as patchy screening. In this talk, I will propose a new "temperature inversion" (TI) estimator to detect this effect. I will show that the estimator is unbiased to foregrounds (CIB, tSZ, kSZ). This is a big advantage over the traditional “quadratic estimator” for the patchy screening which is biased by foregrounds and CMB lensing. I will then present the first detection of the patchy screening effect through cross-correlation of the Atacama Cosmology Telescope and Planck satellite CMB data, and unWISE galaxies. This measurement, exceeding 7-sigma in significance, directly probes the distribution of electrons around these galaxies. I will discuss the prospects of this technique to constrain galaxy evolution models. Finally, I will present a vision for some of the exciting science opportunities to come in the coming decade.