You place a red ball inside of a box, and close the lid. You then place a black ball on top of the lid. A small curtain is used to cover the box. When you drop the curtain, the black ball which had been on top of the box instantly changed places with the red ball inside of the box.
Metamorphosis is the name of a well-known magic illusion.
It is a large-scale effect, and usually performed on stage. The magician raises a curtain, and instantly changes places with his assistant. The performer places three different colored silks inside the transformation tube. The tube is tossed in the air. When reopened, the silks transform into three different color liquids that match the silks.