Complex sentence: Then, they also managed to illuminate the sequence of so-called embryonic'leaflets' that are produced in the newly-recognized organism of the first days of development and from which further development of all other tissues are developed during further development.
Split into simpler sentences: Then, they also managed to illuminate the sequence of so-called. Embryonic leaflets that are produced in the newly-recognized organism of the first days of development and from which further development of all other tissues are developed during further development.