Part I on the history of sleep science in Berlin covered the development from the time of Enlightenment in the 17 century to the period of early physiology at the beginning of the 19 century. From that time on, the medical faculty of the University of Berlin became a leading center of physiology and clinical science in Germany. In the first half of the 20 century, brain research was especially strengthened by the foundation of the Brain Research Institute in Berlin-Buch by the Kaiser Wilhelm Society. Soon after the first few publications by Hans Berger on the electroencephalogram (EEG), Alois Kornmüller and coworkers established a rigorous program of EEG research at this institute. In this context, two different forms of sleep were first recognized in the cat by Klaue in 1936, and the new sleep EEG method was applied in patients with sleep-wake disorders, e. g., narcolepsy. These promising developments came abruptly to a halt on the eve of World War II. After the war and the separation of Berlin, it took more than 20 years until sleep research started again in different academic institutions in East and West Berlin. At the time just before German reunification, four Berlin sleep laboratories were members of the German Sleep Society (DGSM), two located in the eastern and two in the western part of the city. Today ten Berlin sleep laboratories are members of the DGSM. In the future, basic sleep science must be strengthened in order to support the well-developed branch of sleep medicine. [ABSTRACT FROM AUTHOR]