Schlieren Imaging is an optical technique which allows viewers to see physical changes in air which the human eye cannot detect. Like many other imaging techniques, Schlieren Imaging involves a few basic principles such as refraction (how light acts/bends as it changes medium), reflection (the act of light bouncing off of a reflective object such as a mirror), refractive index (the amount light bends as it passes into a certain material) and density (which affects refractive index). A Schlieren Imaging System allows one to see the different densities that light rays from a source pass through: even if not visible to the human eye. One of the most common ways of setting up a Schlieren Imaging System is the “z-style” (as shown in the attached diagram). This includes a single concave mirror, a light source, a knife edge or color filter, and a camera. As shown in the diagram, the light shines onto the mirror, which reflects and focuses the light to a single point onto the knife edge. The knife edge is used to block out light bent at a specific angle due to a density change in its path. This blocking of light creates a dark spot in the image or field of view which gives the image contrast and clarity, alowing you to be able to see the pocket of air of different density.