Mini Review on Transport Coefficients of Quark-Gluon-Plasma

We discuss the development in the field of relativistic viscous hydrodynamics and its application to high energy heavy ion collisions to extract the transport coefficients of Quark Gluon Plasma (QGP). We start with the early developments in the field and continue our discussion to the recent development. We also discuss various uncertainties and a few open problems related to the extraction of transport coefficient of QGP from the experimental data.