The open hardware mobile and modular educational robotic platform Yrobot is a new open platform that has been developed at the authors' department. It features a unique combination of teaching robotics and electronics along with algo-rithms, artificial intelligence and hardware based programming. The original motivation was to encourage students' interest in technical fields of study, to support teaching and the selected areas of the information and communication technologies. As a modular platform, Yrobot system enables development of various interesting and special applications in form of the expansion modules. The development software, support and firmware source code as well as the full hardware designs are available under the free licenses. The design and functionality of the Yrobot mobile and modular educational robotic platform is presented. The developed system is meant to serve as an educational platform for students at the undergraduate and graduate levels.