DNA profiling helps determine a unique DNA profile for an individual by analysing DNA from body tissue. Polymorphic regions contain different sequences, and each person inherits a combination of polymorphisms from their parents. DNA profiles are used in crime scenes, paternity disputes, and disaster victim identification. The history of DNA testing dates back to the 1920s, and methods have evolved to include short tandem repeat polymorphisms. Social issues arise when DNA profiling is used to determine parentage, and opposing opinions exist on the matter.