TITLE Cosmology with the Longest Lever Arm using CMB Lensing ABSTRACT The cosmic microwave background (CMB) provides a snapshot of the universe at a redshift of around 1100. At the same time, it acts as a backlight that is gravitationally lensed by structure that formed at low redshifts. CMB fluctuations are therefore especially sensitive to physics that becomes influential at late-times such as dark energy and neutrino mass. Recent measurements from the Planck satellite indicate a tension between the amplitude of structure measured at low redshifts and that expected from the primary CMB alone. Ongoing high-resolution CMB experiments like the Atacama Cosmology Telescope (ACT) and planned experiments including the Simons Observatory and CMB Stage IV will significantly improve the precision on cosmological parameters and clarify these tensions. I will survey the status and prospects of using CMB lensing in conjunction with low-redshift optical and spectroscopic probes to constrain the properties of neutrinos and dark energy.