Emerging portable smart devices with more functionality demands highperformance, smaller, lighter, thinner, and cheaper electronic components. This is enabled by the transformation of today’s surface-mounted discrete passives such as resistors, capacitors, and inductors as thin films embedded in the package substrate or buildup layers. Such a trend would lead to miniaturized and more efficient power systems. This chapter reviews the fundamentals of materials, designs, and processes for each of these thin-film passive component technologies, particularly focusing on power applications. It then describes the challenges and recent advances in each of these areas.