Chemistry
Electron Density Mapping Using X-Ray Crystallography at Atomic Resolution
Quick fact
A high-resolution X-ray crystallographic experiment can locate even hydrogen atoms, which have only one electron, producing electron density maps with a resolution of ~1 Å. These maps are so detailed that a chemist can 'see' the 3D architecture of the molecule as if reading a topographical map of the atom's electronic cloud.
Why this is interesting
If you shine a beam of X-rays at a crystal, you get a pattern of spots—but how do those spots reveal the very positions of atoms inside a molecule?