Young Johannes Jessenius started studies and met Johannes Kepler. As a field surgeon he took part in war with Turks. Afterwards, he became professor of surgery and anatomy on Vittemberg University, where he met his wife.

Jessenius came to Prague. He was granted an audience with king Rudolf II. He managed to make the first public autopsy in the town. A body for the autopsy had got from hesitating executioner Mydlář. Jessenius became resident in Prague, and thereafter his wife came also to Prague.

Jessenius became physician in Carolinian University and personal physician of king Rudolf II. The plague stroke the town Prague. His healthy wife had been murdered throughout this time. He treated ill king Rudolf, and after his death, he embalmed him.