Let's say you just invented the first universal solvent! What would you keep it in? how would your mythical storage device store it?
There are a few options. Few of them are vacuum, a black hole, anti-matter box, etc.
Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
For controlled fusion they use magnetic fields to keep the plasma away from the sides of the container.
In mathematics, you don't understand things. You just get used to them.