Disclosed herein are fluorescent proteins and Split-Fluorescent proteins (SFPs) including Split-Green Fluorescent Proteins, such as tripartite split-GFPs. Nucleic acid molecules encoding the fluorescent proteins and SFPs, as well as methods of using the fluorescent proteins and SFPs, are also disclosed. For example, methods of detecting protein-protein interactions are disclosed herein.
ACKNOWLEDGMENT OF GOVERNMENT SUPPORT
 This invention was made with government support under Contract No. DE-AC52-06NA25396 awarded by the U.S. Department of Energy. The government has certain rights in the invention.