How do cells figure out how to build three-dimensional organs with multiple kinds of tissues? A group of engineers, geneticists, biochemists and cell biologists at Children’s Hospital Boston and Harvard’s Wyss Institute for Biologically Inspired Engineering sunk their teeth into this mystery – starting, in fact, with the tooth.

Scientists have known for more than a century that the growth of many organs (including tooth, cartilage, bone, muscle, tendon, kidney and lung) begins with the formation of a compact cell mass called “condensed mesenchyme.” But what makes this mass form to begin with? Until now, no one knew. …