A detailed analysis that benefits from a slate of new approximate numerical and exact asymptotic results produces highly accurate properties of the ground state of the harmonium atom as functions of the confinement strength omega and quantifies the domains of the weakly and strongly correlated regimes in this system. The former regime, which encompasses the values of omega greater than omega (crit)approximate to4.011 624x10(-2), is characterized by the one-electron density rho>(*) over bar *(omega ;r(1)) with a global maximum at r(1)=0. In contrast, the harmonium atom within the latter regime, which corresponds to omega < omega (crit), differs fundamentally from both its weakly correlated counterpart and Coulombic systems. Resembling a Wigner crystal of a homogeneous electron gas, it possesses a radially localized pair of angularly correlated electrons that gives rise to rho>(*) over bar *(omega ;r(1)) with a "fat attractor" composed of a cage critical point and a (1, -1) critical sphere. Allowing for a continuous variation in omega, the new compact representation of the ground-state wave function and accurate approximants for the corresponding electronic properties are designed to facilitate the use of harmonium in research on electron correlation and density functionals.