Nanofluid is a mixture of a small concentration of nanometer sized solid particle like nanoparticles, nanotubes or nanowires suspended in the liquid and making a colloidal suspension. It is relatively a new field which is less than two decades old. Nanofluid attracts researchers in many ways for their enhanced heat transfer properties. Nanofluid has better heat transfer performance than the base fluid. This paper represents a comprehensive review on the preparation and stability of nanofluid, maintaining stability, evaluating stability etc. and different thermal physical properties like convective heat transfer coefficient for laminar and turbulent region, thermal conductivity, specific heat capacity, viscosity etc. and some transport phenomena like pool boiling heat transfer, flow boiling heat transfer.