Before Nestlé turned 20 in 1834, he completed a four-year apprenticeship with J. E. Stein, owner of a Frankfurt pharmacy. At some stage between 1834 and 1839 he migrated, for reasons unknown, to Switzerland. At the end of 1839, he was officially authorized in Lausanne, Switzerland, to perform chemical experiments, make up prescriptions, and sell medicines. During this time, he changed his name to Henri Nestlé in order to adapt better to the new social conditions in French-speaking Vevey, Switzerland, where he eventually settled.