Abstract: Atomically thin two-dimensional heterostructure provides an exciting platform to realize strongly interacting electron and hole fluid in the ground state. With the combination of both repulsive and attractive Coulomb interactions, the quantum electron-hole fluid can host a variety of novel correlated phenomena of multiparticle charge complexes. I will discuss the rich phase diagram of the electron-hole fluid, including bosonic exciton fluid, fermionic trion fluid, electron-hole plasma, and different mixture phases. I will also show that optical spectroscopy provides a powerful way to probe the phase diagram as well as transport of the electrons, holes, and excitons in the electron-hole fluid.