Neutron excess in nuclei

Neutron excess in atomic nuclei have challenged our understanding of nuclear structure and the properties of nuclear matter for decades: the existence of neutron droplets have been looked for 60 years, the discovery of neutron halos in neutron drip line nuclei have impulsed radioactive beam physics, nucleus with neutron excess show a shell structure different from the one of stable nuclei, while the spatial distribution of the neutron excess directly connects to the nuclear equation of state at saturation density. Rare isotope facilities have given access to the neutron-rich side of the nuclear landscape. This HFHF colloquium will focus on few of the most recent experiment results in the field: the first observation of an interacting free four-neutron system and the discovery of the 28O unbound system (8 protons, 20 neutrons) at the RIBF, Japan, as well as an introduction to the recently approved PUMA (antiProton Unstable Matter Annihilation) experiment at CERN aiming at using antiprotons to investigate neutron skins.