Muscles provide mechanical forces needed for the dynamic activity of a human body. The mechanical forces applied on various human organs lead to different types of physical movements (e.g., contraction and extension, rotation, and bending). Injuries and diseases can disable muscle functionality, which may lead to the pronounced deterioration of a human activity or even cause death. Surgical correction is not always possible or does not always provide optimal results. Implanted artificial biocompatible devices can replace defective muscles. These should operate locally at the defective site by monitoring the need for a specific physical movement and then applying the correct mechanical force to obtain it. These devices should also be self-energized using the body’s energy resources and programmed for optimal operation. On page 337 of this issue, Yang et al. (1) present a new approach for fabricating thin piezoelectric biocompatible thin films that actuate physical movements, demonstrated on mice muscles, under applied electric field.