Cellular proliferation is an important parameter for many cell and tissue culture experiments. It is often used to characterize the effects of a growth factor, to assess the biocompatibility of a new material or to test the toxicity of a new drug.
The PicoGreen proliferation assay makes use of a dye (PicoGreen) that fluoresces upon interacting with double-stranded DNA (dsDNA). Thus, the fluorescence generated from a sample can be compared with that of a dsDNA standard and used to measure the DNA in that sample. The DNA is assumed to correspond directly with the number of viable cells in that sample.
Here is the PicoGreen dsDNA Assay Protocol.