It was reported that syllabus coverage of fundamental theory and knowledge could sometimes be insufficient in Problem-Based Learning (PBL), resulting in the so called "holes" in the conceptual knowledge base . At the Department of Chemistry and Bioscience in AAU, most of the PBL projects in the chemistry section are research projects, especially experimental projects related with the on-going research that are mainly in the area of applied supramolecular chemistry, disordered materials, and separation processes (). The training in experimental skills and the operation of instruments are crucial and indispensable for completing PBL projects. In most cases, students can effectively carry out their projects in an analogous way by applying the experimental skills and instrumental operation techniques. However, gaps often exist between the theoretical foundation and the practical requirements for performing research projects, highlighting the need to bridge this divide during the learning process. They may know well the "hows" in conducting the project, but not need to know "whys" from the the aspects of fundamental principles. Considering the syllabus of 50 % traditional lecture, the learning of fundamental theories and knowledge is insufficient for students, which also limits their learning depth in chemistry and the exertion of their creativity. Overall, the general pedagogical problem that we targeted was to strengthen in-depth active 95 learning of the fundamental principles and excite creativity in PBL. First principles thinking has recently been introduced into engineering education , which offered a solution to improve the depth of learning and creativity. Hereby we described our recent practice and achievements in strengthening first principles thinking in PBL of chemistry.