5.6: Near-field Scanning Optical Microscopy (NSOM) Near-field scanning optical microscopy (NSOM), also called scanning near-field optical microscopy (SNOM), is a scanning probe technique that overcomes the diffraction barrier in traditional far-field optical microscopy. Conventional optical microscopy techniques are limited by the diffraction of light and the resolution is limited to roughly 250 nm, which make it very difficult to resolve the domains or clusters in the cellular membranes[1]. The basic idea in NSOM is to confine the illuminating light to nanometric dimensions to break the diffraction limit that cannot be achieved by traditional far-field optical microscopy[2]. Thus, NSOM can produce high-resolution topographical and optical images to study biological membranes. Figure \(\PageIndex{1}\) shows the diffraction of light and the near-field in the NSOM fiber probe. Figure \(\PageIndex{1}\).1 Diagram illustrating near field optics. Diffraction of light coming from NSOM fiber probe. Showing wavelength of light and the near-field. Image used with permission (CC BY Unported; Zogdog602). UC Davis ChemWiki is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License. 1