Cho's smile brightened and lit up her face a bit. "Transfiguration. McGonagall set a three and a half foot essay on the elemental properties. It's fascinating, really. Did you know that at the base of every object lies the same thing? And since we are all composed of the same energy and matter, that is how we're able to turn one object into another?" Cho realised that she'd started rambling and quickly shut her mouth, her cheeks going a bit pink. Marietta teased her often about how quickly Cho was able to talk about transfiguration, but being a fellow Ravenclaw, she didn't mind it. But Harry wasn't a Ravenclaw and she didn't want to bore him to tears.