Counting cells. Researcher and a screen showing a stream of cells being counted and sorted. The counting of cells is called cytometry. This is flow cytometry, characterizing each cell as it passes at high speed through a laser beam. Up to 50,000 cells a second can be measured. The scattering of the laser beam provides a way to identify the cells. Many other characteristics, such as shape and surface texture can also be measured. The cell stream is disrupted into drops (lower right) that are electrically-charged to allow sorting and purification. Photographed at Celltech's Slough research laboratories, UK.
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