The capability to perform unmanned reconnaissance in buildings, tunnels, and caves and to contribute to military operations over urban terrain depends upon the availability of a small, quiet aerial vehicle that features highly maneuverable and hovering flight in a single configuration. The Alfred Gessow Rotorcraft Center at the University of Maryland is actively pursuing the development of autonomous micro hovering air vehicles that can carry out such challenging missions. Much of the technology base on micro air vehicles is in its early stage of development and understanding of associated phenomena, necessary design tools and navigational control strategies are not available. There are numerous challenges and barriers that must be overcome before these vehicles can be successfully and efficiently used by armed forces or other civilian applications. Some of the key fundamental issues include: low Reynolds number (low speed) aerodynamics, robust controllers, flight controls, efficient and innovative vehicle designs, efficient power and propulsion systems, compact actuators and sensors, and ultra-light weight and adaptive structures. This presentation will discuss the state-of-art on the developments of micro hovering air vehicles.