This chapter provides an overview of the evolution of transistors, from their initial invention to the cutting-edge devices of today. It begins with the invention of the point-contact transistor and the bipolar junction transistor, followed by the introduction of the MOSFET, which eventually led to the widespread adoption of CMOS technology. The chapter examines key characteristics of the MOSFET and the trends in its scaling over time. It then traces the transition from planar MOSFETs to FinFETs—the first mainstream 3D transistor architecture—and further to the current state-of-the-art GAAFETs. Looking ahead, the next major advancement is expected to be CFETs, which vertically stack p-type and n-type transistors, and then 2D channel FETs anticipated in the more distant future. The cover image of this chapter shows the world’s first 2 nm nanosheet technology by IBM in 2021. Reprint Courtesy of IBM Corporation © 2025.