You will need:
The experiment is similar to growing salt crystals, except the supersaturated sugar solution is hot, so have an adult handy.
Toffee is made from a supersaturated solution of sugar and water. Sugar is dissolved in heated water. When it cools, the sugar crystallises. Seed crystals or a rough string help the crystals nucleate and start to grow – crystals growing from molten rock in a magma chamber work on the same principle.