In the 16th century, a time of superstition and dogma, physician Paracelsus challenged the medical establishment with a radical idea: 'The dose makes the poison.' This is the story of his defiant journey to establish the foundations of toxicology, arguing that any substance, even water, can be harmful in the wrong quantity. Explore how this fundamental principle of dosage and moderation revolutionized medicine and remains a cornerstone of science today.