In this talk I will discuss theories where the weakest of all classical energy conditions -- the Null Energy Condition (NEC) -- is violated. These theories have rather peculiar unintuitive properties and therefore allow for quite exotic cosmological scenarios - bounces etc. providing new theoretical opportunities for the origin of our universe. On the other hand, for the contemporary universe, the NEC can put a bound on non-ideal parts of the Dark Energy's (DE) energy momentum tensor. This talk is based on arXiv:1109.1047 and arXiv:1209.2961.