Seeds as energy storehouse, primarily nourish the developing embryo and sustain the young seedling during germination. In addition, due to their oil, protein and carbohydrate composition, seeds serve as an important food resource for both humans and animal consumption. Legumes seeds and in particular peanuts are inexpensive source of plant proteins and edible oil. Owing to their importance in global food security, it is necessary to understand the genetic, biochemical and physiological mechanisms for better incorporation of the main storage reserves in seeds, such as proteins, fatty acids, starch, and secondary metabolites. This in turn will foster breeding programs producing more efficient and productive peanut genotypes. Here we review the current understanding of seed development in peanut as well as conserved developmental mechanisms between legumes and Arabidopsis. In this talk we will present the biochemistry, genetics, and transcriptional regulation during seed development with emphasis on metabolic pathways of storage reserve biosynthesis. Additionally, we will discuss the effects of drought on seed metabolism, oil quality and composition.