Borexino is a 280-ton liquid scintillator detector placed at the Laboratori Nazionali del Gran Sasso (LNGS), the largest underground laboratory in the world. It is characterised by the best-ever-achieved radio-purity of its construction materials. This was at the base of ground breaking results in the measurement of low energy neutrinos, as geoneutrinos and solar neutrinos. European Physical Society awarded the 2021 Giuseppe and Vanna Cocconi Prize to the Borexino Collaboration for our ground-breaking observation of solar neutrinos from the pp and CNO chains that provided unique and comprehensive tests of the Sun as a nuclear fusion engine. Our group gave key contributions to these results. Borexino ended data taking in October 2021 but the analysis of the data is still ongoing.