No matter who you are; for most of us grey hair is an inevitable part of getting older. But what if you could switch off the gene that causes it? For the first time, scientists have identified a gene called IRF4 as the culprit behind grey hair. The gene IRF4 helps regulate melanin in the body which determines - among other things - hair colour.  Age and environmental factors will influence how quickly IRF4 triggers hair greying.  But the researchers say their discovery could lead to a treatment that could stop it in its tracks.