For example, self-diffusiophoretic Janus motors still rely on fuels that are cytotoxic, and their motion is only indirectly controllable by ratchet mechanisms or chemical gradients.(9) Acid-powered motors based on propulsion by bubble generation are limited to the gastric environment and were not shown to be controllable.(10) Hybrid biomicromotors based on red blood cells functionalized with magnetic nanoparticles could be actuated by ultrasound and steered by a magnetic field and were shown to be biocompatible.(11) However, the movement controllability was fairly limited by the fixed directionality of the ultrasound transducer, and specific, controllable cargo release was not shown. Other hybrid microcarriers that rely on on-board bacterial propulsion have also been shown to be magnetically controllable, but only in 2D and with relatively low propulsion speeds of less than 5 μm/s.(12) Limitation to 2D motion is also the main drawback of a magnetically actuated stick–slip motion microrobot.(13) Martel et al. proposed an approach that relies entirely on magnetotactic bacteria as controllable motor units which showed promising behavior in terms of 3D motion and cargo loading capacity, but suffered from a limited lifetime in physiological conditions and the yet unsolved question of defined cargo release.(14, 15) Nelson et al. employed synthetic microhelices that were able to manipulate microobjects(16) or act as functionalized drug carriers.(17) These motile devices proved to be biocompatible and precisely steerable in 3D. However, it remains to prove that these highly individual motors, that are able to target single cells,(18) can deliver significant drug doses for therapeutic purposes within a reasonable time frame.