A BBC investigation has revealed that children in Indonesia are working in dangerous mines to collect materials used in our gadgets.
Tin is an important element that is used in electronic devices like smartphones and tablets.
In countries like Indonesia, people work in mines to dig tin out of the ground.
It's a dangerous job - but it's even more dangerous if the mine is being run illegally.
Processing plants called smelters buy the raw tin that the miners dig up, and then sell it to gadget companies.
The problem gadget makers face is that they can't be sure exactly which type of mine their tin has come from.
The people who work in the illegal mines say they need the money and have no other choice.
Watch Hayley's report to hear more from them.