In this unit, learning of photosynthesis is triggered by introducing students with the idea of Martian greenhouses for producing oxygen and food for living there. Problem questions relating to how basic conditions for long term living can be created in an artificial environment are posed to students. The solving process is expected to lead to the idea that plants and other organisms are able to carry out photosynthesis thereby providing the station with oxygen and at the same time absorbing carbon dioxide. During the unit they are also expected to answer to the question “How do we know, what we know about photosynthesis?” through researching the development of related scientific discoveries. Through student inquiry the factors that influence photosynthesis are explored providing students with ideas needed for designing their own space greenhouse.