In this article, we address four main questions, including: What is self-regulated learning for? What key strategies do students need to guide and direct their own learning process? What cues in the learning environment trigger self-regulation strategies? What can teachers do to help student to self-regulate their learning, motivation, and effort in the classroom? We illustrate that answers to these questions have changed over time and that changing conceptualizations of the self-regulation process have influenced the assessment tools that were used. We also point to changing classroom conditions as a factor that has affected the assessment of self-regulation. Finally, we formulate some questions that need to be tackled in research on self-regulation and introduce the articles and commentaries in the special issue that provide some cutting-edge work on the use of assessment to register self-regulation over time.