Fluorescence cross-correlation spectroscopy (FCCS) has several applications in the field of biophysics and biochemistry.  Fluorescence cross-correlation spectroscopy (FCCS) is a powerful technique that enables the investigation of interactions between various types of biomolecules, including proteins, nucleic acids, and lipids.
FCCS is one of the few techniques that can provide information about protein-protein interactions at a specific time and location within a living cell. FCCS can be used to study the dynamics of biomolecules in living cells, including their diffusion rates and localization.
This can provide insights into the function and regulation of cellular processes. Unlike fluorescence resonance energy transfer, FCCS does not have a distance limit for interactions making it suitable for probing large complexes. However, FCCS requires active diffusion of the complexes through the microscope focus on a relatively short time scale, typically seconds. FCCS allows for measuring simple molecular stoichiometries and binding constants.