During the past 200 years thermal science and engineering has experienced a remarkable transformation of scale. Principles and theories that had been established in support of steam engine development and design, at the meter and centimeter scale, are now routinely applied to the design and optimization of nanoelectronic devices, at the micron and nanometer scale. This Fourier Lecture will briefly review the genesis and foundations of the heat transfer discipline and its formative years, continue with a recapitulation of the history of the Assembly for International Heat Transfer Conferences, and then delve into the evolution and "inward migration" of thermal packaging of electronics to illustrate this transformation of scale.