 The demonstrations and methods made possible an effort that grew to involve 4 international collaborations of physicists working at CERN's Antiproton Decelerator.In 1999, Gabrielse's TRAP team made the most precise test of the Standard Model's fundamental CPT theorem by comparing the charge-to-mass ratio of a single trapped antiproton with that of a proton to a precision of 9 parts in 1011.The precision of the resulting confirmation of the Standard Model prediction exceeded that of earlier comparisons by nearly a factor of 106.