Hydrogen is the lightest atom. In some molecules, it behaves not like a tiny ball but like a wave that can seep through an energy barrier. It is as if a ball found itself on the other side of a hill without rolling over it. Scientists call this tunneling.

But how does a molecule find a path for such a transition? Previously, we only saw the starting and ending points, while the route itself remained hidden. Now scientists have come up with a method that holds the molecule at the 'seam': the boundary where the initial and final states have equal energy. It is like a tightrope that hydrogen walks along.

Now that we have a map of this invisible path, we can calculate the rates of chemical reactions more accurately. This is important for understanding how enzymes work in our bodies and for designing new materials.