Abstract: A device for fluorescence correlation spectroscopy, especially for multicolor fluorescence correlation spectroscopy, in which light rays are focused in a transparent medium located in a sample vessel. Such device includes a vessel holder in which at least two sample vessels with a focussing reflecting bottom are provided, and a common cover for both sample vessels which is at least partly light-transmitting. In a preferred embodiment, a plunger with a light window facing the bottom is inserted into the sample vessel, and the quantity of transparent medium is selected so that the light window of the plunger is immersed in or wetted by the medium.

Abstract: A fluorescence fluctuation microscope, in which excitation light and detection light are coupled into or out of a microscope by means of a common beam path, comprises a closed loop scanning unit (22, 23).

Abstract: The proposal comprises a module (1) for attachment to a microscope (3), by means of which the said microscope can be used for fluorescence correlation spectroscopy.

Abstract: In the procedure, the light beams are incident parallel to the transparent medium and are deflected toward a focal point inside the transparent medium. This avoids the use of refractive lens systems. The focusing lens system according to the invention enables the bundling of light beams of different wavelength to a point inside the sample. This clearly simplifies the design and adjustment of a multicolor fluorescence correlation spectroscopy device.