“…Fourteen years ago, shortly after our TRAP team captured the first cold p, I hesitated before putting into print the futuristic goal of using these to form H that was cold enough to confine in a magnetic trap for precise laser spectroscopy [1]. In the intervening years, however, our TRAP Collaboration developed the techniques to slow, capture, cool and stack suitable cold p at 4 K [2,3], an energy more than 10 10 times lower than any other source.…”