The Chirikov criterion or Chirikov resonance-overlap criterionwas established by the Russian physicist Boris Chirikov.Back in 1959, he published a seminal article,where he introduced the very first physical criterion for the onset of chaotic motion in deterministic Hamiltonian systems. He then applied such a criterion to explainpuzzling experimental results on plasma confinement in magnetic bottlesobtained by Rodionov at the Kurchatov Institute.