The aim of the book, 11 chapters based on Lena Heine’s PhD thesis, is to investigate how learners mentally deal with content-focused activities in a foreign language by using the concept of problem solving tasks for which subjects do not have any immediate solutions. Through empirical evidence, this valuable contribution provides readers with a better understanding of the role foreign language plays in content and language integrated learning (CLIL) which will be of interest to researchers and instructors in cognitive learning, task-based language teaching, and content-focused courses.