Identical twins are fascinating. Born with the same DNA, they go on to develop both astounding similarities and staggering differences. This groundbreaking film meets some of these amazing human pairs. Millie and Daisy like the same subjects at school and get near identical exam results. Anais and Samantha discovered uncanny similarities in their looks as well as tastes and personalities when they met in their early 20s, despite being brought up by different families in different countries. The film also discovers how twins can be identical but grow up to become very different people - like twins Brenda and Aidan. Born Brenda and Bonnie in the 1960s, Bonnie told her sister she was a lesbian when she was in her 20s and later went on to have a sex change to become Aidan. These remarkable stories shed light not only on what it means to be a twin, but also on what it means to be human.