Already in ancient times there was the idea that tiny animals or insects could cause diseases when ingested or breathed. In parallel, several philosophers developed the concept of seeds to explain the composition of the world. Both concepts were amalgamated in the brilliant idea of seeds of disease that was spread in the famous poem “De rerum natura” by the Epicurean philosopher Lucretius. The idea was refined in the Renaissance by the prominent physician Girolamo Fracastorius with his famous semina morbi (seeds of disease) that explained contagion. The germinal theory of microbes of the s. XIX did nothing more than assign to this already millenary idea a material substratum.