In the particulate matter project (see https://publiclab.org/wiki/pm), we're interested in discerning round, droplet-based particles (i.e. particles that form from condensation nuclei, known as "secondary particles") from jagged and crystalline particles (i.e. particles made from mechanical crushing or combustion debris, known as "primary particles"). The reason we are interested in this is that there are different potential health effects from different types of airborne particles. Near industrial sand mines, airborne respirable crystalline silica is a major concern, as the tiny jagged particles can travel deep into your lungs, cut and scar them, impeding gas exchange between your lungs and blood stream (read more about this here: https://publiclab.org/wiki/silica-monitoring). Mathew Lippincott has done a lot of work taking camera-based microscope images of particles, and it looks like there is the potential to discern round from jagged particles (see this note: https://publiclab.org/notes/mathew/09-03-2015/optical-imaging-of-passive-particle-monitors). Can this be done using DIY microscopes?