here's something i didn't know -- remember the plasma lamps that were popular as novelty items and science displays, a few decades ago? usually shaped as a glass sphere, they featured a single central electrode, and were filled with a mixture of gases (e.g., helium and neon), which were then excited into filamented plasma illumination by introducing a high frequency alternating curent. placing an obect, say a hand, upon the surface of the sphere would alter the electric field, causing a single plasma beam or filament to migrate from the inner electrode to the point of contact.
the plasma lamp was invented by nikola tesla, the genius who spent his life as an inventor and a mechanical and electrical engineer. his patents and theoretical work form the basis of modern alternating current (AC) electrical systems and the AC motor. active into his 80s, tesla was under-appreciated during his life, yet he persisted in his studies. his biography makes for fascinating reading.