In mammals, only 3% of the genome consists of coding genes which, when transcribed into proteins, ensure the biological functions of the organism and the in-utero development of future individuals. But genes do not function alone. They are controlled by other sequences in the genome, called enhancers, which, like switches, activate or deactivate them as required. A team has now identified and located 2700 enhancers — among millions of non-coding genetic sequences — that precisely regulate the genes responsible for bone growth. This discovery sheds light on one of the major factors influencing the size of individuals in adulthood, and explains why their failure could be the cause of certain bone malformations.