Early experimental work on nanofluids¹  reported that the addition of a small fraction of carbon nanotubes (CNTs) to engine oil increased the thermal conductivity of the base fluid by a factor of two to three. Such conductivity enhancements represent significant increases in the convective heat-transfer coefficients of engineering systems, and hold promise for making nanofluids the heat-transfer media of the future. The magnitude of thermal conductivity enhancement was initially characterized as ‘anomalous’ and sparked immense scientific interest during the first decade of the 21st Century. Several laboratories throughout the globe experimented with different types of fluids and nanoparticles. Among the most common base fluids that were investigated were: water; engine oil and other oils; and ethylene glycol. Among the nanoparticles were: aluminium oxide (Al₂O₃); copper oxides (both CuO and Cu₂O); single-walled and multiwalled CNTs; copper (Cu); and gold (Au).