This is a simple device with just 3 components that amplifies currents 1600 times, It uses a neat trick of a transistor amplifying another transistor, otherwise known as the Darlington pair to amplify the MINISCULE current flowing between a persons finger and the ground sufficiently to light a 3mm LED
The transistors are 2N3904 NPN.
•2N3904 Transistor X 2
PDF handout downloadable below:
p.s: too easy for ya?, well its a part of a free, fully documented (programs+schematics) online course designed to get young kids into electronics, so if you think it's any good pass it on?