The introduction of ozone into organic chemistry is due to the work of C. D. Harries, first in Berlin but mainly in Kiel, during the period 1903–1916. He established experimental procedures for ozonolysis, demonstrated the generality of the reaction of unsaturated compounds with ozone, and showed that ozone could be used for the synthesis of a variety of sensitive compounds. Most important for the future development of organic chemistry, he established that ozonolysis could be an important tool for determining the structures of organic compounds. He also initiated investigations into the mechanism of ozone reactions with alkenes, which culminated about forty years later in the Criegee mechanism for ozonolysis.