The dynamics of two-electron atoms

Since the first attempts to calculate the helium ground state in the early days of Bohr{Sommerfeld quantisation, two-electron atoms have posed a serie s of challenges to theoretical physics. Despite the seemingly simple proble m of three charged particles with known interactions it took more than half a century after quantum mechanics was established to describe spectra of t wo-electron atoms satisfactorily. The evolution of the understanding of cor related two-electron dynamics and its importance for doubly excited resonan ce states is described in this overview.