Abstract Microelectromechanical Systems (MEMS) Virginia Chu INESC Microsistemas e Nanotecnologias, Lisbon, Portugal Microelectromechanical systems or MEMS are a class of devices consisting of three-dimensional structures capable of mechanical or electro-mechanical functionality. The fabrication of MEMS utilizes processes based largely on planar silicon microelectronics technology, modified to allow the formation of released 3-D mechanical structures. MEMS devices can usually be put into 3 classes: (1) sensors; (2) actuators; or (3) passive structures. This presentation will be divided into two separate talks as follows: Part 1: I. Introduction and Background II. Applications of MEMS Part 2: III. Technologies for fabrication of MEMS IV. Thin film, large area MEMS V. Future directions  This presentation is intended to be a general overview of the field of Microelectromechanical systems and will introduce the audience to this newly evolving and growing class of devices. For a good introduction to MEMS, see: Nadim Maluf, An Introduction to Microelectromechanical Systems Engineering (Artech House, Boston, 2000).