Flowering plants have evolved as one predominant life form on earth. One common principle of flowering plants and probably one of the main reasons for this evolutionary success is the rapid development of an embryo along with a nourishing tissue, called the endosperm. Embryo and endosperm are surrounded by maternal tissues and build the plant seed. Seeds are a fascinating biological structure and their formation is an essential step in the plant life cycle. Seeds also represent the major food source for animals and humans and for this reason, are an indispensable unit in the ecosystem on earth. Despite its importance, surprisingly little is known about seed growth and further progress for the understanding of seed development appears to be hampered by three major constraints. First, seeds are compound structures comprising different tissues of different origins. For proper development, however, a close coordination between these structures is required. Second, the involved organs and tissues are deeply buried within maternal tissues and thus, they are not easily accessible. Third, the parent of origin for certain regulators appears to be crucial for their expression in the seed and an understanding of the complex chromatin regulation that mediates these gene activity patterns is still at its beginning. Here an interdisciplinary and multi-species project is proposed to overcome these constraints unraveling the molecular mechanism and principles of seed growth control. By analyzing seed development in two distantly related species with a combination of cell biology, biochemistry as well as molecular biology including quantitative genetics and genomics, I will obtain detailed insights into one of the central processes of (plant) life.