Explore the fascinating world of active matter in complex environments through this lecture by Thomas Franosch. Delve into the concepts of circle swimmers, gravitaxis, and the harmonic oscillator as part of a comprehensive research school on active matter. Learn how objects convert energy from their surroundings into directed motion across various length scales, from biofilament-motor protein suspensions to flying birds. Discover the impact of complex environments like soils, oceans, and the human body on individual swim gaits, transport behavior, and collective phenomena. Gain insights into cutting-edge experimental methods, theoretical approaches, and engineering techniques used to study active materials in controlled, complex surroundings. Enhance your understanding of this exciting research topic and its applications in fields ranging from microscopy to microfluidic devices.