Micro-electro-mechanical systems (MEMS) and micro-opto-electro-mechanical systems (MOEMS) packaging are much different from conventional integrated circuit (IC) packaging. Many MEMS and MOEMS devices must interface to the environment in order to perform their intended function, and the package must be able to facilitate access with the environment while protecting the device. The package must also not interfere with the operation of the MEMS or MOEMS device. For example, the die attachmentmaterial should have low stress and low outgassing, while also minimizing stress relaxation over time, which can lead to scale factor shifts in sensor devices. Many devices are application-specific, requiring custom packages that are not commercially available. Devices may also need media-compatible packages that can protect the devices from harsh environments. Techniques are being developed to handle, process, and package the devices so that high yields of functional packaged parts will result. It is the objective of this chapter, in Sec. 11.3, to review and discuss packaging challenges that exist for MEMS and MOEMS and to expose these issues to new audiences from the integrated circuit packaging community. In Sec. 11.4, the objective, in the light of the challenges, is to discuss a case study for packaging design considerations and guidelines for a specific and successful MOEMS, the Digital Micromirror Device.