Module description: Flow cytometry is a technique for counting, examining, and sorting microscopic particles suspended in a stream of fluid. It allows simultaneous multiparametric analysis of the physical and/or chemical characteristics of single cells flowing through an optical and/or electronic detection apparatus. (http://en.wikipedia.org/wiki/Flow_cytometry)

In systems biology flow cytometry can be used for high throughput handling of cells based on some physical properties they have. It could be the cell size or shape or it could be the presence or absence of some particular molecule on their surface, detected by staining.