The objective of this book is to discuss the current status of research and development of boron-rich solids as sensors, ultra-high temperature ceramics, thermoelectrics, and armor. Novel biological and chemical sensors made of stiff and light-weight boron-rich solids are very exciting and efficient for applications in medical diagnoses, environmental surveillance and the detection of pathogen and biological/chemical terrorism agents. Ultra-high temperature ceramic composites exhibit excellent oxidation and corrosion resistance for hypersonic vehicle applications. Boron-rich solids are also promising candidates for high-temperature thermoelectric conversion. Armor is another very important application of boron-rich solids, since most of them exhibit very high hardness, which makes them perfect candidates with high resistance to ballistic impact. The following topical areas are presented: .boron-rich solids: science and technology; .synthesis and sintering strategies of boron rich solids; .microcantilever sensors; .screening of the possible boron-based thermoelectric conversion materials; .ultra-high temperature ZrB2 and HfB2 based composites .magnetic, transport and high-pressure properties of boron-rich solids; .restrictions of the sensor dimensions for chemical detection; .armor