Overview:While the formalism of equilibrium physics is established in an elegant way within the Boltzmannian description, understanding of non-equilibrium systems remains elusive although they are prevalent in nature. For example, nonequilibrium aspects are essential for fluid motions, material failure or sustenance life in a single cell. The last two decades have seen a tremendous growth on this broad theme and lots of efforts have been made to put forward unifying principles and general truths.