This paper represents a comprehensive review on the preparation and stability of nanofluid, the convective heat transfer coefficient and different thermo‐physical properties such as thermal conductivity, specific heat capacity, viscosity, and so on. Here, for each thermo‐physical property, measurement methods, enhancement mechanisms, and criticisms of different studies are also presented. However, based on the available literature, it is concluded that a nanofluid has, in general, better thermo‐physical properties even at a very low particle concentration (typically 1% or less) than conventional heat transfer fluids. The only drawback is high viscosity which leads to a higher pressure drop. At a very low particle concentration, this drawback can be minimized. Three tables are provided for three thermo‐physical properties namely thermal conductivity, specific heat capacity, and viscosity, which can be used as a ready reference for calculating the nanofluid properties.