Though this is the 50th AVS Symposium, RF plasma sources have a shorter history. Their development, driven by the explosive growth of the computer industry, did not really start until the 1970s. There are three main types: capacitive discharges called Reactive Ion Etchers (RIEs), Inductively Coupled Plasmas (ICPs), and the newcomer on the block, Helicon Wave Sources (HWS). Development of RIEs and ICPs has progressed mainly by trial and error, but in the last ten years their evolution has been aided by computer modeling, a result of the fast chips that these sources themselves make possible. From a plasma physics standpoint, each of these sources poses interesting problems. RF energy penetrates into ICPs much farther than skin depth theory would predict. Helicon sources produce much higher densities than ICPs at the same power. RIEs, with all their deficiencies, still perform better in many applications. Are we simply lucky, or are there physical reasons for this?