This protocol outlines how to prepare nano-sized materials for examination using electron microcopy and in particular as an aid for particle size analysis. The type of sample preparation is dependent on the type of material. The protocol subdivides techniques for preparation of wet and dry samples, as well as conductive vs. non-conductive samples. Nanomaterial samples pose challenges when preparing samples for imaging. One challenge is that these materials tend to agglomerate or aggregate and proper imaging of these samples requires special treatment of the samples. One way of handling aggregation or agglomeration is to disperse the samples in a liquid, and spray them on a substrate. Use of a sonic probe may also be used to break up aggregated or agglomerated samples. Another way is to extract the material from the liquid. In selected cases imaging of the nanoparticles is aided through the removal of the solid particles from liquid matrix using an organic solvent. Solid inorganic nanomaterials on the other hand are often poor conductors and as such may need to be coated to passivate the surface so that electrons from the electron beam are carried from the surface. Other materials such as certain metal nanoparticles have been sputter etched to remove the oxide coating on the surface to promote better imaging. Other materials such as carbon nanotubes or other organics and polymers may have a tendency to be damaged during imaging.