Middle Sex features interviews with some of the world's leading experts in the field and examines what their latest research reveals about the key influences that shape sexual identity and orientation. The conclusions are startling.

In the words of neurobiologist James Pfaus, 'There are as many sexual orientations as there are faces. To suggest that the simple categories – male/female, heterosexual/homosexual – are adequate to describe the whole range of human sexuality is to ignore science and the evidence of nature.'

'One thing we have to remember is that variation is the norm,' says sexologist Professor Milton Diamond. 'Biology loves difference. Society hates it.'

Filmed in locations from the Americas to the Far East, Middle Sex is also a fascinating study of repression and denial that reveals the extent to which culture and religion shape, and frequently distort, our attitudes to sex.

Check out the articles on the right for more information about some of the issues featured in the programme and details of the support available.