Abstract: Nuclei with more neutrons than protons tend to get rid of excess neutrons to reach the valley of stable nuclei through beta-minus (β-) decays. On the other side of the valley of stability, proton-rich nuclei follow the analogous process through beta-plus (β+) decays. Beta-delayed proton emission, observed more than 40 years ago, typically occurs in very proton-rich nuclei and not on the neutron-rich side of the stable nuclei.  However, the emission of protons following β- decay is energetically allowed for neutron-rich nuclei with neutrons bound by less than 782 keV.  This condition may be fulfilled in so-called halo nuclei where one or several neutrons are loosely bound and orbit far from the core. ¹¹Be is one of the most promising candidates, resulting in ¹⁰Be following the beta decay to ¹¹B and the subsequent proton emission.  A team of researchers from the National Superconducting Cyclotron Laboratory at Michigan State University and TRIUMF (Canada) carried out the first direct observation of the beta-delayed proton decay of a neutron-rich nucleus by directly measuring the very low-energy protons emitted following the beta decay of ¹¹Be. This experiment was performed with the Active Target Time Projection Chamber (AT-TPC), a gas-filled detector capable of providing high efficiency and resolution for low-energy charged particles such as the emitted protons. In this seminar, I will discuss the technique and the results of such experiment, as well as different aspects of this decay, including a speculative dark matter decay.