Formed when compounds are cooled close to absolute zero.
Idea
Quantum particles consist primarily of two groups - bosons and fermions. Bosons have an integer spin, while fermions have half-spins. According to the Pauli Exclusion Principle, fermions cannot be in the same state or configuration, while bosons can.
Hypothetically, an unlimited number of bosons could share the same energy state, and be mapped out by a single wave function. Einstein also proved that this happens to even-spin bosons at low enough temperatures.