What fair use exceptions are you talking about? There are thousands on fair use exceptions.
Answer:
Nanosecond
Explanation:
Nanosecond is used for measuring DIMM read and write times.
Depends on how deep you're willing to go to really,
You need one of a few arrangements of flip flop circuits to keep 1-bit state.
Going deeper, you need either NAND, or NOR gates(or a bunch of other ones) and connectors.
Even deeper, you'll require diodes or transistors to build the logic gates.
Beyond that is particle physics.