This dissertation contains three essays in development and nutrition. These essays focus on a prevalent health problem in the developing world, undernutrition, which is one of the leading causes of child mortality and leads to poorer health, education, and labor outcomes in adulthood (Ahmed, et al., 2012; Avula, et al., 2013; Black, et al., 2008; Hoddinott, et al., 2013; World Bank, 2017). The first chapter provides an introduction to this dissertation. The second chapter, coauthored with Derek Headey and John Hoddinott, identifies the long-term drivers of nutritional change over the past two decades in 47 developing countries, applying consistent methods on a common database, from which we extracted a common set of nutrition-sensitive factors for all countries. We find that, while the magnitudes vary across countries, wealth accumulation and gains in parental education are the two largest drivers of reductions in undernutrition in the developing world. The variations in the child nutritional returns to parental education can be explained by the availability of public, rather than private, resources—i.e., child nutritional returns to parental education are greater when public resources are more abundant. The third chapter is joint work with Yaeeun Han and Hyuncheol Bryant Kim. This chapter is motivated by the strikingly low dietary diversity among young children in Ethiopia, which increases the risk of chronic undernutrition. This monotonous diet is a consequence of many factors, including poor maternal knowledge of good diets, limited resources, or both. We implemented a clustered randomized control trial that randomly provides nutrition education for mothers (behavior change communication, BCC), food vouchers, or both. We find a reduction in chronic child undernutrition only when both BCC and vouchers are provided, even though BCC alone improves mothers’ nutritional knowledge and child-feeding behaviors to some extent. Food vouchers alone did not have any effect on mothers’ nutritional knowledge or child-feeding behaviors. Our results suggest that, when both knowledge and income are intertwined challenges for improved child-feeding practices, addressing both constraints simultaneously may augment the positive impacts. Using a lab-in-the-field and field experiment settings in the context of a floriculture plant in Ethiopia, the fourth chapter investigates the effects of nutrition on labor productivity and economic decision-making by randomly providing nutritious filling breakfasts to workers. As intermediate outcomes, I also examine to what extent hunger alleviation affects individual’s social preference, attention, and physical ability. I find that farm breakfasts did not improve productivity or economic decision-making. On behavioral outcomes, farm breakfasts decreased stress and increased self-interest and trustworthiness. These effects exhibited a pattern of hedonic adaptation in which effects are pronounced in the first several weeks but dissipate over time. By examining behavioral outcomes related to productivity and economic decision-making, this study shifts the focus from how nutrition affects the physical aspects to the psychological and the behavioral aspects.