The evolution of ever-smaller microfabrication techniques, driven by market demand, has lead to multi-million transistor devices as a single piece part. Complimentary metal oxide semiconductor (CMOS) nanoelectronics will be mass-produced by the year 2004 when lateral structures smaller than 100-nm will become common. Beyond the next ten years the future is less certain, but other technologies such as nanometer-scale single electron transistors provide an idea of what may be possible in 20-to-25 years. Microelectromechanical systems (MEMS), which bring "eyes, ears, noses, and muscles" (sensing and actuation) to electronic systems, are fabricated using similar processes and will benefit from decreasing minimum feature size over time. Nanoelectronics and nanoelectromechanical systems will evolve over the next decade to provide ever-higher levels of functional density per unit area. The continuing increase in functional density will enable decreased spacecraft system size, and ultra-small spacecraft. Examples of prototype microengineered attitude determination and propulsion systems are given.