The paper discusses the MERIA scenario about the construction of the slide in which the students re-invent the concept of the slope of a curve and get introduced to the notion of a derivative of a function. The findings of the paper are based on the implementation of the scenario in associated schools. It is a joint work of six  project members: Rogier Bos, Michiel Doorman, Kristijan Cafuta, Selena Praprotnik, Sanja Antoliš and Matija Bašić.