Portrait of the Swiss alchemist and physician Theophrastus Paracelsus (1493-1541). He was initiated into medicine by his father before entering the University of Basel, Switzerland, in 1510. Paracelsus was mainly an alchemist; he never stopped looking for the Philosopher's Stone which was believed to be an elixir of eternal life. However he is also considered responsible for the transition from alchemy to modern medical chemistry. Paracelsus first recognised that the aim of alchemy was to prepare medicines to treat diseases by studying plant or animal derived compounds.