 In 1882, he moved back to the University of Bonn working with Eduard Strasburger, becoming a private docent.In 1883, Schimper postulated the endosymbiotic origin of chloroplasts and paved the way to the symbiogenesis theory of Konstantin Mereschkowski und Lynn Margulis.In 1886, he was appointed Extraordinary Professor at the University of Bonn, and worked largely on cell histology, chromatophores and starch metabolism.