When people hear the word chemical they usually think of dangerous, toxic stuff. In fact most things around, on and inside of us are chemicals and most of them are absolutely not toxic. But keep in mind that most stuff can be toxic in the right amount. Drink 6 liters of water and you might die, even though we are made up mostly of water. All chemicals work this way, so keep that in mind while doing experiments.
Chemicals for making crystals can range from safe chemicals like table salt and table sugar to very corrosive chemicals like copper chloride and toxic chemicals like potassium dichromate.
To be continued...