The result was a prototype called "MinWin 10." It replaced the classic Explorer shell with a custom launcher (codenamed "Lighthouse"). It ripped out GDI (Graphics Device Interface) and replaced rendering with DirectX 12 Ultra-Lite. The OS booted to a command line in 2 seconds. With a community driver pack, it booted to a desktop in 6 seconds.
It was a failure. (At least, commercially.)
Here is the complete history, architecture, and legacy of the OS that was too efficient to live. To understand Nano 10, you must go back to 2015. Microsoft was terrified of Linux containers. Docker was eating the datacenter. In response, Microsoft created Windows Server Nano —a stripped-down, headless installation of Windows Server 2016. It had no GUI, no 32-bit compatibility, no Local Logon, and no GUI stack at all. It measured roughly 400 MB on disk.