This manuscript presents an interview with John Sweller, Fred Paas, and Jeroen van Merrienboer about cognitive load theory. It presents the views of these main founders of the theory on the progress from the first major publication on the theory in 1998 (Sweller, Van Merrienboer, & Paas, "Educational Psychology Review," 10(3), 251-296, 1998) to the current publication, 20 years later in 2018 (Sweller, Van Merrienboer, & Paas, "Educational Psychology Review," https://doi.org/10.1007/s10648-019-09465-5, 2019). More specifically, the interview focuses on challenges and opportunities of cognitive load theory and the associated instructional design research, the role of measurement of cognitive load and mental efficiency, as well as the instructional control of cognitive load in the cognitive load research. The interview is concluded with suggestions and advice for young researchers. [For "Cognitive Architecture and Instructional Design: 20 Years Later," see EJ1217401.]