Sure, you must wonder: How exactly does this work? How is it even physically possible? There is an explanation, and it's nightmare fuel.
Out of all the characters with big eyes, the ones in anime and manga aimed at little girls are, perhaps, the biggest.
Twitter user Nuron1434 provided the world with, first, this example.
And then, an explanation:
Inside the round circle, it says "eyeball". Above that, it reads "brain".
Some things, including huge cartoon eyes, go best unexplained.