Fluorescent Multilayer Disc, abbreviated as FMD, is a data storage medium that follows the idea previously used in DVDs, making multiple layers to get more data on one disc, but takes the idea to a new level. Because the normal reflective layers were too limiting making it near impossible to get more than two layers on a disc, Constellation 3D decided to find a new way to reflect the light that would not interfere with other layers. To do this, they have a different fluorescent material in each layer which will reflect a different frequency of light than the other layers making it possible to shine the light through the disc and read the proper frequency for the expected layer. Because of this, the main limitation on the number of layers, besides how many different materials can be found to be used, would be to keep the disc from being too thick.
See also Fluorescent Multilayer Card.