In the exploration of space, the launching of Sputnik proved the possibility of sending an object into orbit around the earth. Subsequent development of spacecraft led to the landing of man on the moon with Apollo 11, followed by construction of the space station, serviced by shuttles that could re-enter the atmosphere repeatedly. In the development of fusion reactors, the success of early experimental tokamaks is analogous to the success of Sputnik. The simple drawings of tokamaks in previous chapters resemble modern tokamaks no more than Sputnik resembles Apollo 11. A lot of development has occurred, and a lot more has been learned about toka — maks. There have been both pleasant and unpleasant surprises. There is, however, a big difference between the two programs. In space science, the basic physics — namely, Newton’s laws of motion — were already known; while in fusion, the physics of plasmas and of toroidal confinement had to be worked out first. After the initial successes, there was much more to learn about spacecraft, such as their interaction with the plasmas, solar wind, and magnetic fields in the solar system. This chapter describes what we have learned about tokamaks, once they were up and running.