This is Benedict Cumberbatch’s eye.
If you look closely, you can see that his eye is blue with green around the pupil.
This is an example of an interesting genetic phenomenon known as “heterochromia”.
Heterochromia can be caused by a variety of things. A mutation in the original eye color gene can cause one color to turn into another. Physical injury can also cause discoloration or changing of the iris color. But perhaps the most interesting reason for heterochromia is when the host is a chimera.
It has been discovered that occasionally, when there are two blastocysts (or extremely young fetuses) in the womb together, and one dies or becomes parasitic, the stronger blastocyst will literally absorb the other dead or weakened blastocyst. Recently, it has been discovered that this happens a lot more often than previously thought. In the case of heterochromia and several other interesting conditions, the stronger of the blastocysts accepts the cells from the other into its body, and they often grow and survive.
TLDR; The reason Benedict is so fucking amazing is that, quite possibly, he used to be two people.
Yes. Fucking yes. Just. Yes. Perfect fucking deduction.