We present a theory of pattern formation in growing domains inspired by
biological examples of tissue development. Gradients of signaling molecules
regulate growth, while growth changes these graded chemical patterns by
dilution and advection. We identify a critical point of this feedback dynamics,
which is characterized by spatially homogeneous growth and proportional scaling
of patterns with tissue length. We apply this theory to the biological model
system of the developing wing of the fruit fly \textit{Drosophila melanogaster}
and quantitatively identify signatures of the critical point.Comment: 5 pages, 3 figure