The Birth of Toxicology

Paracelsus, a 16th-century Swiss physician, established the foundational principle: "The dose makes the poison." Water kills if you drink too much. Oxygen becomes toxic at high pressures.

Not every poison hides forever. Alexander Litvinenko was killed in 2006 with polonium-210, a rare radioactive element. Once investigators identified the isotope, its contamination trail became evidence: traces of polonium-210 were found across hotels, restaurants, taxis, and aircraft, letting investigators reconstruct the route taken by the poison and the suspects.