The genes that are involved in the development of the fetus are activated in different tissues and at different times. Their expression is carefully regulated by so-called “enhancer sequences”, which are often located far from their target genes, and requires the DNA molecule to loop around and bring them in close proximity to their target genes. Such 3D changes of the DNA are in turn controlled by other sequences called topologically associating domains (TADs). EPFL scientists have now studied the TADs involved in digit development in the fetus and have gained insights in some of the big questions surrounding them. The work is published in Genome Biology.