He recently taught us what a mole is. I used to think a mole was just an animal like me, but I learned it’s also a way chemists measure things that are so small we can’t even see. A mole of something ...

The SI system includes a hierarchy of units to measure the amount of substance, accommodating a wide range of scales from kilomoles (kmol), which represent thousands of moles, down to picomoles (pmol) ...