Leopold Ruzicka is appointed Professor of Organic Chemistry at the University of Utrecht. Although he is very happy in Holland, after three years he decides to accept the invitation of the ETH to return to Zurich because of the Swiss superiority in chemical industry.

In those years, Leopold Ruzicka receives the support of the oldest perfume manufacturer in the world, Haarman & Reimer, of Holzminden in Germany. While working with odours and essences he discovers that muscone and civetone contain rings of 15 and 17 carbon atoms, respectively. Prior to this finding, it had been generally accepted that rings of more than eight atoms would be too unstable to exist. In 1917 ,he acquires Swiss citizenship.

Leopold Ruzicka works as assistant of Staudinger. Together they enter the quite unexplored field of the active constituents - named by them pyrethrins - of Dalmatian insect powder, a plant product, toxic to insects and other coldblooded animals.

Leopold Ruzicka receives the Nobel Prize in Chemistry that he has won in 1939. Because of the World War II he is unable to reach Sweden. He shares the prize with Adolf Butenandt, "for his work on polymethylenes and higher terpenes." With his work Ruzicka has shown that terpenes and some other large organic molecules are comprised of multiple units of isoprene.

Leopold Ruzicka dies in Mammern in Frauenfeld District in the canton of Thurgau, Switzerland, on Lake Constance.

Leopold Ruzicka joins the Technische Hochschule in Karlsruhe where he receives his diploma and a doctorate in just four years. Among his teachers are Christian Bunte, Carl Engler, Fritz Haber and Hermann Staudinger. Under the guidance of Staudinger, Ruzicka finishes his dissertation on phenyl methyl ketene.

Leopold Ruzicka attends a classical Gymnasium in Osijek, his mother's birthplace. Ružička has moved here after the early death of his father in 1891. In Osijek, Ružička receives also his primary education. During his youth, his dream is to become a priest but, after discovering physics and mathematics, he switches to studying technical disciplines.

Leopold Ruzicka works for a Geneva perfume manufacturers, Chuit, Naef & Firmenich. Here he leads an ambitious research programme involving the synthesis of the sesquiterpene perfumes farnesol and nerolidol and clarification of the structures of four important odorous ketones: civetone, muscone, irone and jasmine.

Leopold Ruzicka is born in Vukovar, Croatia, then part of Kingdom of Croatia-Slavonia, Austro-Hungarian Empire.

Leopold Ruzicka is appointed Senior Lecturer at the ETH.

Staudinger becomes Willstätter's successor at "Eidgenössische Technische Hochschule" (ETH, Swiss Federal Institute of Technology) at Zurich. Ruzicka follows him there.

The firm of Ciba, Basel, becomes interested in Leopold Ruzicka's work on the preparation of quinine-like compounds. With various co-workers, the first synthesis of b-collidine and of linalool, the partial synthesis of pinene, and a series of investigations in the monoterpene field are carried out.

Leopold Ruzicka is appointed Honorary Professor at the ETH.

Ruzicka becomes Professor of organic Chemistry at the ETH. Ciba renews the contact with his laboratory. This association leads in a few years to scientifically as well as industrially important successes in the field of male sex hormones. Ruzicka discovers the molecular structure of androsterone (‘34), progesterone (‘34), and testosterone (‘35). After ‘50 Ruzicka turns to biochemistry, particularly to the biogenesis of terpenes. He publishes with success his hypothesis, Biogenetic Isoprene Rule.