Piezoelectric materials are about as close to magic as you can get. They turn physical pressure into electricity and can even turn electricity into physical pressure - an amazing sort of bidirectional converter for mechanical and electrical energies. Perhaps even more amazing is the fact that you can easily 'grow' your own piezoelectric crystals overnight using just a couple of common ingredients - awesome.
Find more at the Maker Shed: https://makershed.com
Make: Electronics, 3rd Edition: https://www.makershed.com/products/make-electronics-3rd-edition-pdf
Learn more here:
http://makezine.com/video/collins-lab-homebrew-piezo/
