A TEM specimen kit is disclosed, which comprises: (a) a top substrate and a bottom substrate, the top and the bottom substrates being transparent and substantially parallel to each other; (b) a first spacer and a second spacer, located beneath the top substrate and sitting on the bottom substrate, the second spacer being opposite to and spaced apart from the first spacer at a distance of d; and (c) a chamber formed between the top and bottom substrate and between the first and second spacer, the chamber having two ends open to the atmosphere and characterized by having a height defined by the thickness h of the spacer, wherein the height being smaller than the diameter of a red blood cell. Also enclosed are methods for preparing a dry specimen for TEM nanoparticle characterization, and methods for analyzing TEM images of nanoparticles in a liquid sample.