Future space exploration will emphasize on cost effectiveness and highly focused mission objectives. Missions costs are directly proportional to its total weight, thus, the trend will be to replace bulky and heavy components of space carriers, communication and navigation platforms and of scientific payloads. MEMS devices are ideally suited to replace several of these components in the future, first by substituting larger and heavier components (e.g. a gyroscope), then by replacing entire subsystems (e.g., inertial measurement unit), and finally by enabling the microfabrication of highly integrated picosats. This progressive approach will also enable new mission scenarios and more detailed investigations of the space environment and of planetary surfaces. Very small satellites (1 to 100 kg) stand to benefit the most from MEMS technologies because reaching the desired performance levels is only possible using a highly integrated approach. The small satellites are typically used for science or technology demonstration missions, with much higher risk tolerance than multi-ton telecommunication satellites. In addition, the ability to mass produce MEMS components opens a new approach to space exploration in the future by sending constellations of nano and picosatellites into space. Examples of such miniaturization and successful use of MEMS for space and planetary missions are described in this paper.