That's not a caterpillar. What you're seeing are images taken using an atomic force microscopy (AFM) showing -- for the first time ever -- an electron in orbit around the nucleus of an atom.
These images aren't just modern-looking works of art; they confirm what physicists had only hypothesized and modeled until now. Gizmodo has more:
An atomic force microscope was used to capture the electron pathways, presented as darker gray bands in the other two images at center and upper left. As a quick refresher on AFMs, they're the microscopes that use atom-sized needles to measure individual atoms that pass underneath the pointy end.
Dvice.com explains more about how the AFM works:
It's like a very very very very very small bit of charcoal that you can rub on tracing paper placed over a surface to view carved patterns that you wouldn't otherwise be able to see.
To operate, the tip of the AFM (probe) moves across a surface, and when it encounters an atom or a molecule, the tip bumps up a little bit as it passes over. This jiggles a laser beam, which records precisely how much the tip was deflected. By making a bunch of passes, the AFM can gradually build up a sort of topographic map of a surface. It's also possible to place a single atom on the very tip of the AFM's probe, and by watching how that atom interacts with the atoms that it passes over, you can tell what's underneath.
Dvice.com goes on to explain how electron's "orbits" are more like waves and there is a certain probability that an electron will exist in more than one spot at once:
Carbon dioxide atoms have a very distinctive pattern of electron orbitals of their own, and by watching how those orbitals interact with a molecule, the researchers were able to make a map of where there definitely weren't electrons, and that let them estimate where the actual electron orbitals were and generate an image.
The image above is a pentacene molecule with its electron orbit pathways. The abstract published in nature says that using AFM will be useful for studying molecular structures, molecular bonding and chemical reactions at the molecular level, among other applications.