Learn exactly how transistors work. http://www.talkingelectronics.com/projects/200TrCcts/200TrCcts.html
How to make a circuit that will allow you to use dead batteries to power your electronics. The Joule Thief circuit explained. http://graywolfsurvival.com/2491/the-joule-thief-a-preppers-best-friend-for-dead-or-homemade-batteries/
BIKE FLASHER - Amazing! This bike flasher uses a single transistor to flash two white LEDs from a single cell. And it has no core for the transformer - just AIR! By Collin Mitchell - 30 LED Project.