This is a program to investigate ultra-cold atoms near the ionization threshold. Rubidium atoms will be chilled using laser techniques, followed by excitation just below the ionization limit to produce a gas of ultra-cold Rydberg atoms or ionization just above the threshold to produce an ultra-cold plasma. Once these states are reached, atomic interactions and plasma physics will be explored in this entirely new parameter space of extremely low kinetic and potential energies. Collective effects are expected to emerge for the Rydberg species, while the ionized state should demonstrate properties of a strongly-coupled neutral plasma.