Russian botanist Konstantin Mereschkowsky was the first person to discover the chloroplast. His discovery was the result of his work with lichens. In 1905, he began arguing for the symbiotic origin of the chloroplast and nucleus.
The botanist discovered chloroplasts as he was studying Andreas Schimper's work with photosynthetic organisms. Mereschkowsky was also the first scientist to propose the theory of symbiogenesis, the process by which larger, more complex cells evolve from their relationship with less complex cells. In 1909, his paper "The Theory of Two Plasms as the Basis of Symbiogenesis, a New Study or the Origins of Organisms" was finally published.