  We discuss microscopic mechanisms of complex network growth, with the special
emphasis of how these mechanisms can be evaluated from the measurements on real
networks. As an example we consider the network of citations to scientific
papers. Contrary to common belief that its growth is determined by the linear
preferential attachment, our microscopic measurements show that it is driven by
the nonlinear autocatalytic growth. This invalidates the scale-free hypothesis
for the citation network. The nonlinearity is responsible for a dramatic
dynamical phase transition: while the citation lifetime of majority of papers
is 6-10 years, the highly-cited papers have practically infinite lifetime.
