Middle of line (MOL)
Beginner
The small set of steps that connect the finished switches to the wiring above them.
Novice
The contacts and local connections that join transistor sources, drains and gates to the first metal layer. Once a few simple steps, it became its own module as transistors shrank.
Expert
In ASAP7 it is three layers: gate and source/drain local interconnect (LIG, LISD) and V0 up to M1, all printed with EUV.