I'll only say a few sentences on this because it's rather high level, but in strongly interacting condensed matter systems something called 'topological order' can occur. The ground state of a many body system (ie a macroscopic one) can have long range entanglement, such that every particle is entangles together. These systems can have some weird emergent properties, like Fractional Qiantum Hall Effect; simplifying quite a lot, in this the particles behave as in they have fractions of an electron charge.

For these systems the interesting thing isnt necessarily learning about their existing interactions (after all it's just electrons and electromagnetism) but what weird emergent properties are visible. Systems like this have some potential applications in Quantum Computing: this talk https://m.youtube.com/watch?v=smX2lSyi2js explains a little.