The primary focus of this book is the phenomenon of breastmilk insufficiency. As we might expect, the concept of breastmilk volume is as puzzling to breastfeeding mothers as it is to researchers, since the amount of breastmilk an infant consumes when breastfeeding is generally impossible for the breastfeeding mother to know exactly. So, the phenomenon of breastmilk insufficiency is basically the perception by the mother of not having enough breastmilk for her infant at some point during lactation. The implication of this perception can be devastating when mothers eventually stop breastfeeding altogether. Unfortunately, the perception of breastmilk insufficiency is increasing worldwide, and, more than ever, we need to understand the causation of the phenomenon to take concrete measures to curb it. There is also a need to examine variation in breastfeeding patterns in different cultures. Many academic studies and popular media seek to ascertain the prevalence of breastfeeding but lack details on various aspects of breastfeeding structure and culture. One consequence of not having a well-defined description of local breastfeeding structure is the difficulty in comparing studies. This book's specific aims are threefold: first, to elucidate, define, and analyze the phenomenon of breastmilk insufficiency. Second, to show breastfeeding data from a Latin America region -for scholars to have more data to examine breastfeeding's human ecology. Third, to share the first-hand methodology and fieldwork techniques used for many years, that can be replicated in further research.