Lei Liu is a managing senior research scientist coleading the K–12 Learning, Teaching, & Assessment center at ETS. She earned a Ph.D. in educational psychology with a focus on learning sciences and educational technology from Rutgers University. Her research interests at ETS lie at the intersection of science learning and assessment, learning sciences, and educational technology. She has been leading multiple projects that capitalize on what is known about cognitive processes, epistemic practices, and peer-to-peer communication with two distinct foci: foundations to define what is and how to measure science proficiency (e.g., a science competency model, three-dimensional learning performances, learning progressions, collaborative problem-solving) and classroom innovations to support learning and teaching (e.g., virtual labs, simulations, conversation-based assessments, automated scoring, and feedback). She has led multiple federal grants to develop transformative innovations for science learning, including an Institute of Education Sciences grant on developing and validating crosscutting concept learning progressions (#R305A170634), a National Science Foundation (NSF) grant on automated diagnosis of student reasoning patterns in science (#2000492), and a National Assessment of Educational Progress (NAEP) Survey Assessment Innovations Laboratory project on developing a virtual science lab. She has produced more than 50 peer-reviewed publications. She is a member of the editorial board of Instructional Science and has served as a reviewer for multiple international conferences, journals, and NSF merit reviews. In addition to her lead role in research, Liu has also been a key contributor to support various operational works at ETS including the California Science Test and NAEP science and mathematics programs.