The Quantitative Biology Initiative (QuantBio) brings together students and faculty from diverse departments and research labs to answer longstanding questions in biology. We are particularly interested in understanding how molecular networks make decisions that determine the fate of cells, how proteins self-assemble into cellular components, how cells self-organize into living organisms, and how collections of cells adapt to changes in their environment. We answer these questions by developing new experimental tools, predictive mathematical models, and computational methods for analyzing large data sets. QuantBio is also a community whose members teach and learn from one another.