  We show that multiscaling properties of developed turbulence in shell models,
which lead to anomalous scaling exponents in the inertial range, are determined
exclusively by instanton dynamics. Instantons represent correlated extreme
events localized in space-time, whose structure is described by self-similar
statistics with a single universal scaling exponent. We show that anomalous
scaling exponents appear due to the process of instanton creation. A simplified
model of instanton creation is suggested, which adequately describes this
anomaly.
