UV Transilluminators are basically used in molecular biology labs to observe DNA (or RNA) that has been set-apart by electrophoresis through an agarose gel. During or right after electrophoresis, the agarose gel is stained with a fluorescent dye that binds to nucleic acid. Disclosing the stained gel to a UVB light source causes the DNA/dye to fluoresce and become visible. This method is used wherever the researcher requires to be able to view their sample, for instance sizing a PCR product, purifying DNA segment after a restriction enzyme digest, quantifying DNA or verifying RNA integrity after extraction.