You might think there are just three different eye colours – brown, blue and green – but in reality our eyes come in a whole spectrum of different shades made up of these colours.
Eye colour is directly determined by the amount of melanin, or brown pigment, in the iris, and this is determined by a combination of genes because eye colour is a polygenic trait.
In the past scientists used to think that eye colour was determined by a single gene and followed a simple inheritance pattern in which brown eyes were dominant to blue eyes.
But according to more recent research, the eye colour inheritance is more complicated than originally suspected because multiple genes are involved.
A common myth is that parents who both have blue eyes cannot have a child with brown eyes because of dominant and recessive genes, but in reality genetic variations sometimes produce unexpected results.
Though there is a less than 1% chance of blue-eyed parents having a brown-eyed child, it is not out of the question.