Statistical Physics
"More is different," P.W. Anderson, Science 177, 393 (1972)
"The chemical basis of morphogenesis," A.M. Turing, Phil. Trans. Roy. Soc. 237, 37 (1952)
(inhibitors and activators with different diffusion rates)
Less can also be different:
"Purely stochastic binary dicisions in cell signaling models ... ,"
M.N. Artymov, J. Das, M.K., and Arup K. Chakraborty, PNAS 104, 18958 (2007)