Researchers from Princeton University and Germany's Max Planck Institute for Dynamics and Self-Organization report the first purely physical experimental evidence that chimera states can occur naturally within any process that relies on spontaneous synchronization, including clock pendulums, lightning bugs and heart valves. A chimera state arises among identical, rhythmically moving components when a few of those parts spontaneously fall out of sync while the rest remain synchronized. The researchers developed a simple apparatus made of two swings, each fitted with 15 metronomes (above). A spring connected the swings so that they moved together. When the swings were set in motion, the metronomes would eventually move together. Yet if the connecting spring was at a certain tensity, the symmetry spontaneously broke so that the metronomes on one swing stayed in lockstep (left) while the metronomes on the other swing moved erratically (right) despite the metronomes all being set to move at the same pace.