The operation of miniaturized vehicles that perform tasks and interact with living cells inside the human body appears to be one more 20th century dream that today’s engineers finally become ready to tackle. In recent years, numerous approaches have emerged from various laboratories to employ such micromotors that can be powered and controlled on a scale that allows them to assist or interfere with cellular processes.(1-3) Most of these micromotors are directly inspired by their natural counterparts which are, for example, flagella or cilia of living microorganisms.(4, 5) These nature-approved propulsion strategies were mimicked successfully with the help of external power sources like electric or magnetic fields, ultrasound, light, or chemical fuels.(6-8) However, carrying out tasks in the complex surroundings of living cells requires more than just miniaturized motion alone. For example, the most prominent micromotors application up to date, the loading with drugs for targeted transport and release, is still far from being realized clinically, due to various shortcomings of current microcarrier systems. The two main challenges are precise, active transport in three dimensions and biocompatibility. Active transport of microscopic cargo should be reasonably fast, and complex microcarrier movements should be directly controllable both spatially and chronologically. In addition to these microengineering aspects, the operation in biologically active environments brings about a whole new set of problems that involves interactions with living matter that mostly happen on the nanoscale. Biocompatibility in this case not only means that the synthetic microcarrier must not be toxic to cells but also implies that the microcarrier has to actively take part in cellular and biomolecular interactions in order to fulfill its task as biosensor, drug distributor, or microsurgeon.