Supercritical angle fluorescence microscopy (SAF) is a technique to detect and characterize fluorescent species (proteins, biomolecules, pharmaceuticals, etc.) and their behaviour close or even adsorbed or linked at surfaces. The method is able to observe molecules in a distance of less than 100 to 0 nanometer from the surface even in presence of high concentrations of fluorescent species around. Using an aspheric lens for excitation of a sample with laser light, fluorescence emitted by the specimen is collected above the critical angle of total internal reflection selectively and directed by a parabolic optics onto a detector. The method was invented in 1998 in the laboratories of Stefan Seeger at University of Regensburg/Germany and later at University of Zurich/Switzerland.