What is the principle of flow cytometry? and what is forward and side scatter?

Flow cytometry is a technique that analyses single cells or particles while they flow past lasers, while they are suspended in a buffer solution. the cells can be analysed for light scatter and fluorescence. light scatter is measured in two different directions: forward scatter (FSC) which indicates the relative size of the cell and the side scatter (SSC) which is the scatter at 90 degrees and indicates the internal complexity or granularity of the cell.