Twelve years have passed since VMware engineers first virtualized the x86 architecture. This technological breakthrough kicked off a transformation of an entire industry, and virtualization is now (once again) a thriving business with a wide range of solutions being deployed, developed and proposed. But at the base of it all, the fundamental quest is still the same: running virtual machines as well as we possibly can on top of a virtual machine monitor.We review how the x86 architecture was originally virtualized in the days of the Pentium II (1998), and follow the evolution of the virtual machine monitor forward through the introduction of virtual SMP, 64 bit (x64), and hardware support for virtualization to finish with a contemporary challenge, nested virtualization.