in neuroscience, including new techniques for recording neuronal activity. Advances in robotic technologies are also vital to achieving these goals, including the development of better-fitting devices and more precise sensing and actuation embedded in devices to target the distal degrees of freedom of the upper and lower limbs that are most likely to facilitate a return of function and independence. Last, advanced control algorithms that can more precisely characterize the patient’s capabilities in real time and not only adjust the level of support needed to complete movements but also impose appropriate resistance or challenge are needed. Capsule robots At the dawn of the new millennium, Given Imaging (now Medtronic) introduced wireless capsule endoscopy as a minimally invasive method of inspecting the gastrointestinal tract. The possibility of collecting images deep inside the bowel just by swallowing a “pill” revolutionized the field of gastrointestinal endoscopy and sparked a brand-new field of research: medical capsule robots. It was quickly understood that conventional capsule endoscopes, which move passively through the gastrointestinal tract, were limited in their inability to interact with the bowel and carry-out interventions. A natural first approach to addressing this was to adopt “on-board actuation,” actively controlling the capsule using internal, miniature locomotion mechanisms (e.g., legs) (42). However, enthusiasm for this approach declined rapidly as the research community realized a major challenge: Integrating complex mechanisms, including an adequate power supply, into a “pill-sized” device (typically 24 mm in length and 11 mm in diameter) was an impractical solution using available technology. The alternative approach of magnetic actuation was explored to solve this limitation. The use of magnetic coupling bypasses the need for intricate mechanisms and reduces on-board power needs and hence the overall size and complexity of the device. This form of actuation manipulates the capsule (containing an embedded magnet) via an externally generated magnetic field. This mechanically simple arrangement can precisely control capsule orientation and induce relative motion. The field may be generated by permanent magnets or electromagnets. In comparing the two, electromagnets provide an additional degree of control in varying the magnitude of magnetic field, although the volumetric magnetic flux density generated is lower than that of permanent magnets. Medical capsule robots are now a clinically viable alternative to standard interventional endoscopy. While offering an elegant mechanical solution, researchers in the area were faced with the challenge of developing reliable control strategies—a complex task owing to the highly nonlinear properties of magnetic fields. These evolved from manual manipulation of a handheld external permanent magnet to robotic control of the magnetic field (43, 44). This was shown to be both clinically and commercially effective for the exploration of the stomach and is now available in hospitals (NaviCam, ANKON). Effective interventional capabilities using magnetic actuation were successfully demonstrated in pill-size robots by combining it with soft robotics. A smart, compliant device operated by external magnetic fields showed the feasibility of actively moving to a site of interest and delivering a drug (45) or collecting tissue biopsies (46). With a market pressure toward ease of use, combined with the complexities of magnetic actuation, the role of robot assistance in magnetic control of capsule endoscopes increased substantially. A key enabler for this was the introduction of real-time localization techniques. Knowing the position and orientation (i.e., pose) of the capsule is crucial to plan the application of magnetic force and torque for the desired motion (47). Clinically viable examples of localization are mainly based on magnetic localization (48). This is now enabling researchers to explore different levels of computer assistance, moving toward the ultimate goal of making endoscopy as intuitive as driving a car in a videogame. Downloaded from https://www.science.org on November 16, 2021 Dupont et al., Sci. Robot. 6, eabi8017 (2021) 10 November 2021 SCIENCE ROBOTICS | REVIEW 9 of 15 As we begin the next decade, intelligent magnetic control of pill-sized robots may offer unprecedented diagnostic and therapeutic capabilities when combined with multimodal imaging (e.g., multispectral, autofluorescence, and microultrasound) and micro/ nanorobotics. Aside from the clinical uses, this could provide a research platform to reach deeper into the human body to address other scientific questions related to, for example, our microbiome. The future may also hold exciting advances in energy storage or wireless power transfer, which revive on-board actuation approaches or “multiscale operation,” as suggested in (46), where a pill-sized robot deploys an army of interventional microrobots. Whatever lies ahead, medical capsule robotics remains an exciting, fast-moving, and highly influential field of research. Magnetic actuation for medicine Long before magnetic fields were used to create images of the inside of the body, they were used to perform surgery. Evidence of the use of magnetic fields for extracting iron shavings accidently embedded within the