The physical program of the A1 collaboration with its 50 members from 20 countries is focused on hadron structure.
A photon incident on a nucleon couples to the nucleon electromagnetic current causing it to radiate mesons if the photon energy is sufficiently high.
The X1 collaboration develops at MAMI brilliant novel radiation sources, and explores their potential for applications.
The atomic nucleus is a bound state of protons and neutrons so called nucleons. The A4 collaboration is investigating the structure of these nucleons.