GitHub is where people build software. More than 150 million people use GitHub to discover, fork, and contribute to over 420 million projects.

In several cases, for example, BCD and DPP, morphogens form exponential gradients 14, 15, 17 and are in steady state 17, 18 (Box 1). However, departures from this theme have also been reported 19.

Our list of the best Lego sets for adults includes awesome kits that'll get you nostalgic, keep you busy and look fantastic on display.