Cereal crop plants have some of the largest and most complex genomes among all plant species. We use genomics to study the composition of cereal genomes with a particular focus on the role that domestication and modern breeding had on genome dynamics. Beside the major cereals wheat, maize, and rice that are grown on large acreages, dozens of minor cereal species are grown for local consumption, often by smallholder farmers. Despite being of minor importance for global agriculture today, some of these minor cereals hold the potential to make a significant contribution towards solving the most pressing challenges of agriculture in the 21st century. This is because many of the minor cereal species are highly adapted to marginal agricultural environments, which is of particular importance for agriculture in desert environment. We are using genomics to understand this adaptation to marginal environments.