Until recently, imaging of individual atoms in a quantum gas microscope had only been achieved for bosonic species. EU-funded researchers have for the first time captured fluorescence images of ultracold fermionic potassium atoms.
Electrons, protons, neutrons and even quarks are all fermions – in other words, particles with half-integer spin. Unlike bosons with integer spin, fermions cannot occupy the same quantum state. This simple fact leads to the structure of elements where electrons have to occupy different orbits around the atomic nucleus.
Further details: A quantum gas microscope for fermions