juha and egg

Juha was taking a walk with his son; after a few minutes they saw an egg lying on the ground.
in this time the boy asked his father:
- how do the birds get into the egg?
Juha said: you add another problem son answered: why father?
Juha replied: I've been asking myself all my life how the birds got out of the egg and now here you are giving me another problem to solve!