Figure 1. Experimental induction of cell death. Necrosis can be induced by multiple freeze-thaw cycles using liquid nitrogen. In this setting, both the plasma and nuclear membranes are ruptured so that cellular contents leak out and only membrane debris are left. Apoptosis can be induced by radiation with UV light or γ rays. The membrane of apoptotic cells undergo specific alterations, but (at least initially) it remains intact. Eventually, apoptotic cells also lose membrane integrity, a setting that is often referred to as late apoptosis or secondary necrosis.