Critical thinking is recognized as a key skill of the 21st century. The basis for the development of critical thinking can be integrated scientific disciplines and the associated scientific method. The learning model should be based on the essence of science as a process of discovering something new and teaching materials should become simulators of 'making discoveries' by recreating the situation of scientific search. The article describes a relatively new type of educational materials - natural-scientific cases (NSC). NSC is based on real-world problem situations, which are solved with the help of a chain of tasks that guides the student along the path of the scientific method. The formulations of the tasks are aimed at the development and diagnosis of critical thinking. An experiment on the introduction of cases into the educational process of two Moscow universities is described in the article. The results obtained indicate that the use of a set of NSC has a double positive effect: the natural science complex serves as an excellent basis for the development of critical thinking, and an increase in the level of thinking contributes to a more productive assimilation of natural science material.