Photograph of a plasma globe: A glass sphere filled with a mixture of noble gases and a high-voltage electrode centred in the sphere. Plasma filaments form appearing as beams of coloured light. These filaments extend from the inner electrode to the glass insulator and can be influenced by conductors approaching the globe, e.g. a hand.
The plasma globe was invented by Nikola Tesla while experimenting with high-frequency currents and studying high voltage phenomena.
(With material from wikipedia.org.)