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What is FCS?

Fluorescence correlation spectroscopy (FCS) is a powerful single-molecule detection technique that measures and correlates fluctuations in fluorescence intensity within a very small detection volume (on the order of femtoliters). This section introduces the physical processes and mathematical theory that govern FCS.

Creating the very small detection volume:

• What is the Confocal Volume?

Correlating fluorescence intensity fluctuations:

• What is Correlation?
• What is Autocorrelation?
• What is Cross-correlation?

Causes of fluorescence intensity fluctuations:

• What Physical Processes Cause Fluorescence Fluctuations?
• How are Physical Parameters Extracted from FCS Data?

For detailed derivations of mathematical equations used to describe FCS, please see Mathematics of Autocorrelation.