What role do our genes play in building our human identity, with us all being similar yet different?

To find out about the biological identity of humans, we have to go through the skin, penetrate the tissues and cross the cell membranes than cores imprisoning our DNA, which contains our genes.
What can we see in our genes ?
Do genetics affects our physiognomy?
And what about our behaviour or our most marked character traits, such as intelligence, language ability, emotionalism, sexuality, etc.?