CNST Nanotechnology Seminar Series. Silicon is best known for the central role it plays in microelectronics and solar energy conversion devices. However, the same electronic and optical properties that make this semiconductor so useful for these solid-state applications can also be useful in medicine. This presentation will discuss how the properties of silicon might be harnessed for the diagnosis and treatment of diseases such as cancer, macular degeneration, and traumatic brain injuries. In particular, porous nanoparticles made from silicon will be discussed. The combination of both nanoscale morphology (e.g. tunable micro- and meso-pore dimensions, capacity to host and protect drugs, polymers, or nanoparticles) and nanoscale properties (e.g. photoluminescence, photonics, chemical reactivity) generates exciting opportunities not readily achieved with other materials.