Tunneling, a key feature of quantum mechanics, is when a particle that encounters a seemingly insurmountable barrier passes through it, ending up on the other side. A series of experiments carried out by physicists from Griffith University, Lanzhou University, the Australian National University, Drake University and Korea’s Institute for Basic Science has definitively determined the tunneling delay, which is also the time it takes for an electron to get out or ionize from a hydrogen atom.