The Paul Scherrer Institute PSI is the largest research institute for natural and engineering sciences based in Switzerland, conducting cutting-edge research in three main fields: matter and materials, energy and the environment and human health. PSI develops, builds and operates complex large research facilities. Every year, more than 2400 scientists from Switzerland and around the world come to PSI to use their unique facilities to carry out experiments that are not possible anywhere else. PSI is committed to the training of future generations.