A wide array of new and exciting methodologies have recently been introduced that are now collectively termed superresolution microscopy and feature both lateral and axial resolution measured in the tens of nanometers and even less. The common thread in all of the these new techniques is that they are able to resolve features beneath the diffraction limit by switching fluorophores on and off sequentially in time so that the signals can be recorded consecutively. Among the methods that improve resolution by PSF modification, the most important techniques are referred to by the acronyms STED (stimulated emission depletion), GSD Ground State Depletion, and SSIM (saturated structured illumination microscopy). Techniques that rely on the detection and precise localization of single molecules include PALM (photoactivated localization microscopy) and STORM (stochastic optical reconstruction microscopy).