What is super-resolution microscopy?

Super-resolution microscopy is defined as any type of microscopy which surpasses the resolution limit of conventional light microscopy by at least a factor of two. There are various types of super-resolution microscopy, and each follows their specific mechanisms in how they function. Some common examples are STED, and SIM. STED involves a method known as spatially patterned excitation. Two lasers are utilized on the focal plane. The excitation laser and the STED laser together diminish the effective point spread function (PSF). A lower PSF is correlated with a higher resolution. This type of microscopy functions by suppressing excited-state fluorophores found nearby to the focal point. This process is known as stimulated emission. It forms a ring-shaped pattern around the center of the image where fluorophores are inactive, while leaving the center unaffected. This results in a PSF that is lower than the diffraction limit of light, enhancing resolution. Highly sensitive photon detectors are then used to capture signals emitted specifical by fluorophores in the center region of the image.  

Structured illumination microscopy (SIM) is utilized to increase the spatial resolution of light microscopy. It works by exciting a fluorescent sample several times with distinct striped illumination patterns. The orientation and location of the stripes are altered every time. The stripes interact with the high-frequency light as the sample is excited. This process results in a third pattern which is more straightforward to analyze. By combining several images, more detail is achieved and an image is regenerated with higher resolution.