The picture tells the story. The magician shows a nickel, quarter, penny and dime to a spectator. Placing the coins in a spectator's closed fist, he requests that the volunteer squeeze them together tightly.
When the spectator's hands are opened, the dime has been turned into a miniature version of its former self! It's teeny tiny! Everything can now be examined.
The trick is practically self-working and can be performed minutes after you open the package.