ETH Zurich appointed Scherrer to the post of Professor of Experimental Physics in 1920, at the early age of 30. In 1925, he organised the first international conference of physicists to take place after the First World War. He became Principal of the Physical Institute at ETH in 1927 and focussed its direction on nuclear physics, a research branch that was still coming into being at that stage. The first cyclotron at ETH Zurich was built under his direction in 1940.