The miniaturization of optics has not only led to novel micro-optical components and systems but has also allowed the integration of micro-optics with the technologies which have been established for micro-mechanics, micro-fluidics and micro-electronics. The MEMS field, which now encompasses much more than `micro electro mechanical systems', has profited significantly from the inclusion of optical functionality, and the label `optical MEMS' (OMEMS) is now well established as a designation for complex microsystems which include optics but also possibly mechanics, fluidics, magnetics and a variety of other technologies. The IEEE/LEOS International Conference on Optical MEMS and their Applications is one of the premier venues for presenting the newest results in this dynamic and rapidly growing field. The 10th Optical MEMS Conference, held in August 2005 in Oulu, Finland, was attended by more than 150 researchers from 20 countries. Presentations focused on basic technologies, including micro-mirrors, scanners and actuators, materials and fabrication techniques and a variety of applications areas, including adaptive optics, sensors, bio-molecular systems, optical networks and communications. The wide spectrum of expertise in evidence at this four-day event reflects the diversity of technologies and applications relevant to the optical MEMS field and the long Finnish summer nights provided ample time and opportunity for animated interdisciplinary discussion. This special section features a selection from the more than 100 papers presented in Oulu. Some of the topics addressed include novel actuation mechanisms for micro-mirrors, including micro-pneumatics and bi-morph actuation, new types of tunable semiconductor lasers, tunable gratings and MEMS-based optically-pumped atomic clocks. The applications areas considered are similarly broad, comprising free-space optical communications, biological sensing and optical data storage. It has been a pleasure serving as Guest Co-Editor for this special section and I look forward to seeing further excellent work from the optical MEMS community.