1. A system for measuring a morphological parameter of a cell comprising: a substrate containing first and second microfluidic channels dimensioned to carry cells therein; 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 pump configured to flow a plurality of cells into at least one of the first and second microfluidic channels; 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 imaging device configured to capture a plurality of image frames of the cells passing through the extensional region at a rate of at least 1,000 cells/second; and at least one processor configured to calculate a morphological parameter of each cell passing through the extensional region, wherein the cells are flowed through the extensional region and the morphological parameter comprises a measured dimension or dimensional change of the cell passing through the extensional region.