Scientists generally imagine atomic nuclei to be more or less spherical clusters of protons and neutrons, but always relatively chaotic. Experiments at the Argonne National Laboratory, inspired by physicists from the Institute of Nuclear Physics of the Polish Academy of Sciences in Cracow, are trying to verify this simple model. To deploy an astronomical analogy, in as much as the majority of nuclei are similar in outline to rocky objects like moons or asteroids, then the nuclei of lead-208 under certain conditions resemble planets surrounded by a dense atmosphere that can move around a rigid core.