Tsui, tsoo ee, Daniel Chee (1939-...), a Chinese-born American physicist, shared the 1998 Nobel Prize for physics with Robert Laughlin of the United States and Horst Stormer of Germany for their discovery of a new form of matter in which it seemed that electrons--the particles making up electric currents--had been divided into parts. Tsui made the discovery with Stormer and Laughlin explained the results of their experiments.