The particles themselves may be too small to see. You will be using a Virtual Microscope (VM) to look for the tracks made by the particles rather than the particles themselves. The tracks are just below the surface of the aerogel. The field of view of the Virtual Microscope is 480 microns wide by 360 microns high, similar to the size of a grain of salt. There are one million microns in a meter (one thousand microns in a millimeter). To get a sense of the scale of the focus movies you will be viewing with the Virtual Microsope look at the images below of a quarter and a human hair as seen under a microscope at increasing magnification.