Indoor localization and tracking has a wide range of applications, including emergency response, E911, personal navigation in large public places (such as shopping malls and museums), asset tracking in warehouses/hospitals/factories, elder care, and the Internet of Things (IoT). NIST extensive research activities in this area include development of new solutions as well as rigorous testing of indoor localization and tracking systems based on the international standard ISO/IEC 18305. We are interested in hybrid localization methods for solving this challenging problem using a variety of sensors and technologies, such as RF-based techniques, inertial sensors, imaging techniques, ultrasound, altimeters, and magnetometers. Cooperative localization techniques are also important. We are interested in not only improving the location accuracy of localization methods, but also doing so in such a way that the resulting systems would not be too expensive or difficult to use.