Years ago I bought a "potato clock".
This strange device made a circuit with a digital clock attached by two wires to a potato (though it also worked well with cola). The potato or cola could provide enough energy to run the clock for a while.
How did it work?
I presume that if you used more or bigger potatoes you could run something more powerful.
Has anyone studied this phenomenon?

I found the answer to this question, and many more, at "Last-word", mmm - from a scientific point of view:
I just love it!