Optical phantoms are a widely used tool to validate optical instrumentation. In essence, phantoms are “false tissues” made of various materials and can be liquid, solid, or gelatinous. Generally, phantoms are made to either simulate a tissue’s optical, mechanical, chemical, or physical properties, or a combination of these. These structures are typically comprised of a base substrate material, which can be doped with certain additives that give the material specific optical, mechanical, or chemical properties. Additionally, depending on the substrate material used and desired geometry, optical phantoms can be molded into a variety of shapes and sizes for different applications.