The invisibility cloak that allowed Harry Potter to wander unseen through the halls of Hogwarts is no longer confined to the realm of fiction.

It sounds like magic, but involves what are known as metamaterials, invented by Muggles (as non-wizarding folk are called in J.K. Rowling's books).

But it is not quite a match for the imagination of Ms. Rowling. In her books, Harry Potter's cloak is so thin, it fits in the inside pocket of his jacket. The real-life version would probably be quite a bit bulkier, Sir John says.

In the novels, Harry can see his silvery cloak, which he inherited from his father. But you wouldn't be able to see one made out of a metamaterial, Sir John says.

The young wizard can also see where he is going while wearing the cloak; that wouldn't be possible in the real-life version, Dr. Eleftheriades says.