In order to better understand heat transfer from chip junctions (heat sources) to the ambient or coolant, one must have a clear picture of the construction of the chip packages. This chapter is to review the detailed chip packaging technology and other level packages of electronic equipment so that the heat transfer paths from the chip junctions to the ambient or liquid coolant and other surrounding structures of the system can be clearly identified. Then proper heat transfer schemes or technologies can be employed to every level of the system thermal design.