The picture (left) shows the 40-45 nm diameter focal fluorescent spot of the isoSTED microscope as compared to the focal fluorecsent spot of a (highest end) confocal microscope (shown are sections containing the optic axis). The fundamental reduction in size of the fluorescent spot enables a much higher spatial resolution in 3D.
The picture (right) shows mitochondrion with nanoscale resolution. The TOM20 mitochondrial complex in red and a protein from the inner part of the mitochondrion in green.
Image credit: Stefan Hell