There is no shortage of technologies being developed to address problems in places like sub-Saharan Africa, India and Bangladesh. Rather, there has been a surge in technology-based international NGOs and many students, researchers and academics have begun thinking increasingly about the global applications of their research. With such an influx of valuable technologies, we face a challenging question:  which technologies offer the greatest opportunity to improve the lives of the poor?  As an institute that develops technologies for emerging markets, LIGTT deals with this question daily. Specifically, we ask questions such as: -  Should we support the development of portable ultrasounds for expectant mothers? Or should we invest first in a low-cost test     for anemia? Or neither? -  Should we develop a household water purification system or focus on community level systems? Or is the water purification     problem a behavioral challenge as opposed to a technological one? -  Do we engineer the next generation of no-flush toilets? Or should we develop microbes that rapidly decompose sewage water? In this seminar, we will discuss how LIGTT approaches these problems and some of the answers that we have come to. We will also discuss how we have taken these questions and formulated them into a formal study to identify the “50 Most Critical Scientific and Technological Breakthroughs for Global Development,” which has already been used to inform strategy decisions at major Global Development agencies such as USAID.