The main goal of this Interlinked Research Project (IRP) is to gain insight in the development of creative problem solving—one of the least well-studied 21st-century skills. The IRP comprises two PhD projects that study creativity (specifically: divergent and convergent thinking) in the context of upper-elementary mathematics and science education. Both projects first examine how creative problem solving relates to children’s domain-specific skills in either mathematics (project 1) or science (project 2). To do justice to diversity, the influence of child characteristics such as working memory span, reading comprehension, and socioeconomic background will be included. Next, a series of four quasi-experimental studies will be performed to examine how creativity can be improved during math and science lessons taught to heterogeneous groups of learners. These studies aim to identify the most predictive and teachable skills to enhance creative problem solving in math and science, compare the effectiveness of different instructional methods to strengthen these skills, and examine whether acquired skills transfer across domains. The results of all six studies will be synthesized in a new theoretical framework that combines creativity with prevailing views on math and science learning. Practical implications will be provided for math and science teachers to enhance the development of the creative potential of diverse groups of learners.