Ever suffered an identity crisis? Ever asked "who am I"?
Despite God unleashing his plagues on Egypt Pharaoh still refuses to let the Israelite people leave. So God has one final plague to unleash on Egypt, one which is nearly incomprehensible in its devistation.
And yet we see in this event God sowing the seed amongst his people of what he does and how he does it which will come to define the identity of Gods people and prepare them for what He will do in the future.