Microrobots (from several millimetres down to a few micrometres in all dimensions) are constructed of nanoscale or molecular components and include various types of magneto-aerotactic bacteria microrobots, nanomotors, biohybrid magnetite microrobots, DNA nanorobots, soft-bodied robots and soft matter. Microrobots may enable applications in cargo delivery, targeting cancer, cellular manipulation and killing cancer. Microrobots swarms exhibit a variety of intriguing collective behaviors, and will serve as a functional bio-microrobot system for cancer "subtle therapy".