The children filed into the classroom, quieter than they’d ever be again, Albus knew. The first-years were always a little awed by their first day at Hogwarts.

“You may take whatever seats you like,” he said.

When they’d all settled, more or less, he said, “I am Albus Dumbledore, and I will be your Transfiguration teacher for at least the next five years. Assuming I don’t manage to get myself the sack before then.”

The children shifted uneasily, but he smiled at them to let them know it had been a joke.

He came out from behind the desk and leant against it—a casual posture meant to put the students at ease.

“The textbooks will tell you that Transfiguration is the art and science of changing one thing into another thing. They are half right.”

The students perked up at the prospect of a teacher criticising their textbooks.

“It is indeed both art and science, but it has little to do with changing things. Rather, Transfiguration is a drawing out of that which is already there.

“At its most basic, it is simply a rearrangement of atoms to form molecules that represent new structures. Do you all know what atoms and molecules are?”

Only one hand rose, belonging to a pale girl with long black plaits.

“Yes, Miss . . . ?”

“McGonagall, sir.”

“Miss McGonagall. Can you provide us with a definition of atoms and molecules?”

“I think so, sir. Atoms are the tiny bits of matter that make up . . . well, everything. They come together to form molecules, which have the chemical properties and can have chemical reactions, so they’re part of everything that’s alive, and a lot of things that aren’t alive.”

The other students looked at her as if she’d just turned into a hydra. She seemed unaware of their reaction.

Albus smiled at her reassuringly. “An excellent explanation, Miss McGonagall. Five points to Gryffindor.”