Summary: The structure of the Casparian strip was first described by the German botanist Robert Caspary in the 19th century. The function of the Casparian strip as an apoplastic barrier for solute transport is now fairly well understood. However, up to now the formation and the development of the Casparian strip is still an open question not only for plant physiologists but also for plant morphologists. Therefore, in the following I will try to rise some new questions and I will try to point out some new experimental approaches, which will be necessary in future in order to find answers to these questions concerning Casparian strip formation and development.