Parylene is the generic name for members of a unique family of thermoplastic polymers that are deposited by using the dimer of para-xylyene (di-para-xylylene, or DPXN). It is first commercialized by the Union Carbide Corporation as early as in 1956, but even today its use has been mainly limited to protective coatings of electronic components, medical instruments. Recently, however, parylene has become an emerging polymer MEMS material for various applications. This paper then reviews the related parylene MEMS technologies, material properties, and applications that were done in our Caltech lab. First, parylene is widely available through a unique room-temperature, pinhole-free, and conformal CVD deposition method, originally developed by William F. Gorham in 1950s. This benign parylene preparation process makes it a suitable technology for post-CMOS integration. Material wise, parylene has rather low melting temperature around 300 C, but it is rather inert and biocompatible. More importantly, we have shown that it is straightforward to make parylene thin film with a tensile intrinsic stress by controlling the last thermal steps. This feature allows free-standing parylene MEMS structures in many designs. As a result, we have successfully developed a multi-layer parylene MEMS technology including buried metal layers. For the last few years, we then have demonstrated various parylene MEMS applications including microstructures, micro sensors and actuators. In this paper, we will discuss parylene-based filters, neurocages, flow sensors, pressure sensors, accelerometers, bolometers, valves, pumps, etc. However, it is our belief that the brightest future of parylene MEMS is for fully integrated systems that can perform complex functions such as our on-going projects like retinal implants and labs on-a-chip.