The point of a microkernel is to keep the underlying structure small and uniform. What you put on top of the microkernel is what defines your operating environm

The point of a microkernel is to keep the underlying structure small and uniform. What you put on top of the microkernel is what defines your operating environment--not whether or not it's a microkernel underneath. For example, Gnu Hurd and Mach microkernel systems run a microkernel. OS X is a Mach-derived system, in fact, IIRC. NeXTSTEP was a microkernel, also Mach-based. Minix 3 is largely microkernel in nature. https://en.wikipedia.org/wiki/Category:Microkernel-based_operating_systems https://en.wikipedia.org/wiki/Category:Microkernel-based_ope... (I ran QNX on a desktop for awhile, in fact, as well as more-normal ones.)