As of my last knowledge update in October 2021, one of the most recent advancements in microscopy was the development of "super-resolution microscopy" techniques, such as the use of STED (Stimulated Emission Depletion) microscopy and PALM (Photo-activated Localization Microscopy). These techniques allow scientists to observe structures at the nanoscale level, surpassing the diffraction limit of traditional optical microscopes.
However, if you're looking for the very latest discoveries or developments in microscopy beyond that date, I recommend checking recent publications in scientific journals or news from research institutions as advancements in technology occur frequently. There might also be innovations like cryo-electron tomography, novel imaging methods, or advancements in AI-assisted microscopy that were developed after 2021.