NY Times has a great article on makers who create tiny replica engines –
DOWNSIZING may be a chilling concept nearly everywhere, but not in the workshop of George Luhrs, a machinist in Shoreham, N.Y., with an affinity for the very small. Mr Luhrs has built a single-cylinder engine you could lose in a pocketful of nickels and dimes. The piston of Mr. Luhrs’s itsy-bitsy engine rides in a cylinder whose bore is just 1/8-inch across. The engine’s stroke — the distance that the piston travels up and down inside the cylinder — is only 5/32 of an inch. The spark plug? You could lay seven of them across the face of a dime and still see F.D.R. peeking through.