During his time at University of Karlsruhe from 1894 to 1911, Haber and his assistant Robert Le Rossignol invented the Haber–Bosch process, which is the catalytic formation of ammonia from hydrogen and atmospheric nitrogen under conditions of high temperature and pressure. This discovery was a direct consequence of Le Châtelier's principle, announced in 1884, which states that when a system is in equilibrium and one of the factors affecting it is changed, the system will respond by minimizing the effect of the change. Since it was known how to decompose ammonia on nickel based catalyst, one could derive from Le Châtelier's principle that the reaction could be reversed to produce ammonia at high temperature and pressure (a process that Henry Louis Le Châtelier had even tried himself but gave up after his technician almost killed himself, due to an oxygen intake related explosion).