Arsenic trioxide is a chemical that can be very dangerous if you touch it or breathe it in. It's made up of tiny particles that can hurt your body if you're not careful.
Doctors sometimes use arsenic trioxide to help patients with a certain type of cancer called acute promyelocytic leukemia. This is a special kind of chemotherapy that can help kill cancer cells.
But even though it can be helpful in certain cases, you should never touch or breathe in arsenic trioxide for fun or without a doctor's permission. It's important to stay safe and not play with dangerous chemicals.