  A growing neutrino mass can stop the dynamical evolution of a dark energy
scalar field, thus explaining the 'why now' problem. We show that such models
lead to a substantial neutrino clustering on the scales of superclusters.
Nonlinear neutrino lumps form at redshift z \sim 1 and could partially drag the
clustering of dark matter. If observed, large scale non-linear structures could
be an indication for a new attractive 'cosmon force' stronger than gravity.
