GATE is a Geant4-based advanced opensource software developed by the international OpenGATE collaboration and dedicated to numerical simulations in medical physics, in particular medical imaging and radiotherapy. Using an easy-to-learn macro mechanism to configure simple or highly sophisticated experimental settings, GATE now plays a key role in the design of new medical imaging devices, in the optimization of acquisition protocols and in the development and assessment of image reconstruction algorithms and correction techniques. It can also be used for dose calculation in radiotherapy experiments. With the GATE-RTion project, GATE recently became a major tool for dosimetric applications in Light Ion Beam Therapy facilities equipped with the Pencil Beam Scanning delivery technique. Find out more on GATE-RTion website.