I have had a love of the tesla coil for a very long time. I'm not sure when it began but it was either in junior high or early on in high school.
Basically in a tesla coil you take some low voltage power source and step it up to a few kv which isn't hard. The really nifty part is where you then take that few kv and you run it through a spark gap and into the primary coil of a second transformer. The reason that this is all nifty like is because the spark takes an extremely small amount of time and has a waveform that has lots of very high frequency components. Because of this the output of the secondary coil gets a big kick both in voltage and in frequency. So you can run a tesla coil with good old 60 hz and get 10 khz out of the secondary coil. I haven't really given much thought to the design of tesla coils for the last couple years and it just sort of makes me happy that I understand the dynamics so much better now.