In their Nobel Lectures of 1956, the two cardiopulmonary physiologists André Cournand and Dickinson Richards described the future projects that they considered important for rounding up their impressive scientific achievements. One of them called for work that brought together structure and function of the lung in a systematic way. They challenged a young anatomist to undertake this in their cardiopulmonary laboratory at Bellevue Hospital. The first steps established the need for quantitative information on the structures that form the pulmonary gas exchanger as well as the airway tree. This resulted in a new approach to lung anatomy: morphometry would provide the quantitative information for modeling structure-function relations in the lung, and eventually in the entire respiratory system, thus allowing a rational analysis of how structures affect or limit functions.