*currently on sabbatical at Skolkovo Institute of Science and Technology Resent progress in fabrication technology led to the rapid development of the new field of metamaterials. Growing interest to metamaterials is motivated both by their potential applications and challenges driven by their unusual properties. Negative index of refraction is one example of such properties. Unusual behavior of metamaterials in the linear regime naturally leads to a question on what are relevant nonlinear properties of such materials. We will present brief overview of modification of well know nonlinear effects and describe new nonlinear effects in metamaterials.