He is best known for his 1837 discovery of Purkinje cells, large neurons with many branching dendrites found in the cerebellum. He is also known for his discovery, in 1839 of Purkinje fibres, the fibrous tissue that conducts electrical impulses from the atrioventricular node to all parts of the ventricles of the heart. Other discoveries include Purkinje images, reflections of objects from structures of the eye, and the Purkinje shift, the change in the brightness of red and blue colours as light intensity decreases gradually at dusk. Purkyně also introduced the scientific terms plasma (for the component of blood left when the suspended cells have been removed) and protoplasm (the substance found inside cells).
Purkyně was the first to use a microtome to make wafer thin slices of tissue for microscopic examination and was among the first to use an improved version of the compound microscope. He described the effects of camphor, opium, belladonna and turpentine on humans in 1829, discovered sweat glands in 1833 and published a thesis that recognised 9 principal configuration groups of fingerprints in 1823.
Purkyně also recognised the importance of the work of Eadweard Muybridge. Purkyně constructed his own version of zoetrope which he called forolyt. He put nine photos of him shot from various sides to the disc and entertained his grandchildren by showing them how he, an old and famous professor, is turning around at great speed. (Souček, 1963).
He was one of the best known scientists of his time. Such was his fame that when people from outside Europe wrote letters to him, all that they needed to put as the address was "Purkyně, Europe".