Imaging nanoscale objects usually requires expensive electron-beam microscopes since the wavelength of visible light is too long--between 400 and 700 nanometers. Now, features as small as 3 nanometers can be imaged with inexpensive optical microscopes using an algorithm that subtracts the differences between multiple exposures, thereby determining the shape of the object so that the image can be reconstructed. The National Institute of Standards and Technology (NIST) developed the technique, called Through-focus Scanning Optical Microscope (TSOM) imaging. It works by taking multiple out-of-focus images at different focal lengths, then stacking them on top of each other.
Text: http://www.eetimes.com/showArticle.jhtml?articleID=212000350
