To provide a video system for achieving the real-time observation of cells of an organism in vivo, a method of observing cells of the organism using the video system, and an endoscope for observing cells of the organism.

The video system comprises an objective optical system with an imaging magnification of larger than 1, a video module 2 with an illumination optical system, and a light source 1 for supplying illumination light. The light source 1 in the video system has a wavelength zone selecting means 8 for dividing the illumination light in a blue wavelength zone or in a red wavelength zone from among the illumination light in the blue, green, and red wavelength zones into two wavelength zones T1 and T2, and blocking the wavelength zone T1 near the green wavelength zone.