With the wide variety of tools currently available and in the works, scientists can assess apoptosis in individual and populations of cells, in samples from live animals to formalin fixed and paraffin embedded (FFPE) microtome slices. They can use light or fluorescent microscopes, flow cytometers, or spectrophotometers. And they can interrogate parameters ranging from RNA and protein expression, to histone modification, to plasma membrane phospholipid orientation, to membrane potential.