Fluorescent Multilayer Disc (FMD) is an optical disc format developed by Constellation 3D at early 2000's that uses fluorescent, rather than reflective materials to store data. Reflective disc formats (such as Compact Disc and DVD) have a practical limitation of about two layers, primarily due to interference, scatter, and inter-layer cross talk. However, the use of fluorescence allowed FMDs to operate according to the principles of 3D optical data storage and have up to 100 data layers. These extra layers potentially allowed FMDs to have capacities of up to a terabyte, while maintaining the same physical size of traditional optical discs.