Quantum level
From Memory Alpha, the free Star Trek reference
The quantum level is a term used for activity that takes place on a sub-atomic scale. This quantum scale is so small, compared to normal physical bodies, that Earth scientists didn't discover it until centuries of developing physics and technology.
As a measure for the difference between normal and quantum scale, Planck's constant is sometimes quoted.
In 2370, in a quantum reality where Captain Picard was killed by the Borg, Commander Data explained to Lieutenant Worf and Captain Riker the properties of the quantum level, when it was discovered that Worf was moving through different quantum realities. (TNG: "Parallels")
