You might be forgiven for thinking that what you're seeing here is a very well-constructed toy. But it's also a fully operational watt balance, the tool that's used to set the standard measurement of a kilogram.
How do you weigh an atom? To be honest, that's a question with plenty of problems which need answering, but one thing's certain: you need some accurate scales. Now, scientists have made a set that can measure the smallest unit of mass, the yoctogram—which is less than the mass of a single proton.