Recent advances in the use of fluorescence spectroscopy to study protein interactions have primarily involved combinations of classic fluorescence techniques, novel probe and coupling chemistries, and advances in laser excitation and detection capabilities. For example, new coupling strategies for fluorescent probes have allowed the first determination of the DeltaG° describing the insertion of a protein into a membrane. Fluorescently labeled oligonucleotides with specific protein-binding sequences have been used to study both protein-DNA associations and oligonucleotide hybridization using anisotropy changes. The first kinetic data describing a DNA-protein binding event was collected with stopped-flow fluorescence instrumentation. Combining scanning fluctuation correlation spectroscopy with a two-photon excitation source improved this technique so that it may now be used to study protein self-associations.