  The discovery of superfluidity in 3He in 1971, published in 1972, [1, 2] has
influenced a wide range of investigations that extend well beyond fermionic
superfluids, including electronic quantum ma- terials, ultra-cold gases and
degenerate neutron matter. Observation of thermodynamic transitions from the
3He Fermi liquid to two other liquid phases, A and B-phases, along the melting
curve of liquid and solid 3He, discovered by Osheroff, Richardson, and Lee,
were the very first indications of 3He superfluidity leading to their Nobel
prize in 1996. This is a brief retrospective specifically focused on the AB
transition.
