We're running out of helium

Helium is the second-lightest element. And it is one of the rarest elements on planet earth. It's the most widely-used of the inert gases. Used in arc welding, diving, growing silicon crystals, and as a coolant in MRI scanners.

In addition to being rare, helium is a non-renewable resource. The helium that we have was produced by the radioactive decay of rock, long ago. Once the gases is leaked into the atmosphere, it's light enough to escape the Earth's gravitational field so it bleeds off into space, never to return. We may run out of helium within 25-30 years because it's being consumed so freely.
Without helium the magnets in the large Hadron collider will not be able to work.