how to make joule thief

while searching on the internet i found a strange project that you can run with it a 3v led with only
1.5v or lees its said even if the battery is almost dead so i tried to make it and its worked

so how to make it  its need simple components 

what you wil need:

1- a transistor any npn one can work bearing in mind the place of base and collector and the emitter

2- toroid with two lengths wires you can find it on an old radio 
3- 1k resistor
4- led that do not run with 1.5 volt
5- your battery

the circuit :

try it and comment
thanks