In the early 1990s, as I began exploring ways to apply nanotechnology to heat transfer engineering, I saw the possibility of breaking down the century-old technical barriers of conventional solid-liquid suspensions by stably suspending nanoparticles. During the past decade, a series of pioneering experiments have discovered that nanofluids exhibit a number of novel thermal transport phenomena. Nanofluids are of great scientific interest because these new thermal transport phenomena surpass the fundamental limits of conventional macroscopic theories of suspensions. Furthermore, nanofluids technology can provide exciting new opportunities to develop nanotechnology-based coolants for a variety of innovative applications. As a result, the study of nanofluids has emerged as a new field of scientific research and innovative applications. The nanofluids review paper in this issue of Heat Transfer Engineering reports on the current status of nanofluids production; shows verified parametric trends and magnitudes in thermal conductivity and heat transfer enhancement in nanofluids; and assesses the current status of nanofluids applications. This paper also points to future research direct ions to achieve ultrahigh heat transfer enhancement.