Dynamic DNA nanotechnology involves the creation of nanoscale devices made of DNA whose primary function arises from their ability to undergo controlled motion or reconfiguration. In the past two decades, dynamic DNA nanotechnology has evolved to the point where it is now being employed in devices intended for applications in sensing, drug delivery, computation, nanorobotics, and more. In this review article, we discuss the design of dynamic DNA nanodevices and the characterization and prediction of device behavior. We also identify a number of continuing challenges in dynamic DNA nanotechnology and discuss potential solutions to those challenges.