Winner of the Nobel Prize for Physiology or Medicine in 1948 for his discovery of the efficiency of DDT as a pesticide.

Born in Switzerland he attended Basle University, gaining his doctorate in 1925. He embarked on a career at J. R. Geigy, the Swiss chemical company, as a research chemist.

Muller's early research concerned vegetable dyes and natural tanning agents. He also investigated disinfectants, moth-proofing agents for textiles and pesticides.

In 1935 Muller started searching for the 'ideal' insecticide - one that could kill numerous insect species without damaging plants and warm-blooded animals. It should be chemically stable, long-lasting and cheap to produce.

Four years of intensive work led to the synthesis of DDT (dichlorodiphenyltrichloroethane). Although the compound had been invented by an Austrian chemist in 1873, it had never received any attention. Field trials now showed it to be effective against a wide variety of pests including the common housefly, louse, Colorado beetle and mosquito.

DDT was hailed as a miracle compound. It seemed to fulfil all of Muller's criteria. For more than 20 years it was the most widely used insecticide. The risks associated with it were not widely disclosed until Rachel Carson published her groundbreaking book, Silent Spring, in 1962.