1. A system for measuring a change in a morphological parameter of a cell comprising: a substrate containing first and second microfluidic channels; an extensional region comprising an intersection of the first and second microfluidic channels, wherein the first and second microfluidic channels intersect in substantially opposite directions; a focusing region located in at least one of the first and second microfluidic channels upstream of the extensional region, wherein the focusing region focuses cells passing there through into a stream of cells located along one or more lateral streamlines; at least one outlet channel coupled to the extensional region; an optical collector configured to capture multiple records of diffracted or refracted light from each cell passing through the extensional region; a pump configured to flow a plurality of cells into at least one of the first and second microfluidic channels and through the extensional region, wherein the plurality of cells flow through the extensional region and are not trapped therein with each cell passing through the extensional region in less than 500 μs; and at least one processor operably coupled to the optical collector and configured to calculate a change in a morphological parameter of each cell passing through the extensional region based on the multiple records, wherein the change in the morphological parameter comprises a dimensional change of each cell passing through the extensional region.