Paracelsus, a Swiss physician and alchemist from the 16th century, is often hailed as the "father of toxicology." He famously stated, "All things are poison, and nothing is without poison; only the dose makes a thing not a poison." This concept, known as the dose-response relationship, forms the foundation of modern toxicology. Paracelsus' work emphasized the importance of dose in determining the toxicity of a substance, a principle that continues to guide toxicological research today.
