This course is designed for clinicians, researchers, and students concerned with understanding functional motor behavior. The material is appropriate for participants at all levels. Effective clinical practice requires more than standardized test batteries and qualitative assessments. Clinicians and researchers must understand functional motor behavior in real time and how it changes with development, natural experiences, and intervention. But such knowledge has proven elusive. This course will: (1) illustrate the power of video—alone and in combination with other technologies and machine learning—to capture the richness and complexity of behavior and critical details of the surrounding context; (2) describe the use of head-mounted eye tracking to record the visual world of infants, children, and caregivers from a first-person point of view, and how visual access changes with disability; and (3) describe tools for annotating video to quantify changes in behavior in real time and over development. Although much of the available data comes from typically developing infants and children, we will also include examples from children with disabilities, and all the material is relevant for healthy and clinical populations across the lifespan. Overall, this course will expand participants’ ability to capture, quantify, and thus better understand motor behavior.