With the increasing scalability of semiconductor processes, the higher-level of functional integration at the die level, and the system integration of different technologies needed for consumer electronics, System-in-Package (SiP) is the new advanced system integration technology, which integrates (or vertically stacks) within a single package multiple components such as CPU, digital logic, analog/mixed-signal, memory, and passive and discrete components in a single system.This book focuses on electrical and layout perspectives, as opposed to discussing thermal and mechanic characteristics of SiP. It first introduces package technologies, and then presents SiP design flow and design exploration. Finally, the paper discusses details of beyond-die signal and power integrity and physical implementation such as IO (input/output cell) placement and routing for redistribution layer, escape, and substrate. It is an invaluable reference for EDA researchers, professionals and graduate students.