Ian listened to the explanation about today and decided this would be a good time to pull out his potions notebook. It had the cumulative knowledge he had gleaned for the last 3 plus terms. He opened it and prepared to take notes. He also pulled out his textbook just in time to hear the professor's question. Ian raised his hand and waited while others answered. When it was his turn, Ian answered,
It's a combination of ingredients with different properties that produce a reaction, hopefully the desired reaction. It's very similar to work in chemistry amongst muggles, sir.