Equations describing Grand Unification theories.
A Grand Unification theory was any idea proposed which offered hope of marrying General Relativity and quantum mechanics.
In 2367, after having his intelligence drastically increased through an encounter with a Cytherian probe, USS Enterprise-D engineer Reginald Barclay spent an entire night debating the finer points of Grand Unification with a holographic Albert Einstein. (TNG: "The Nth Degree")