Odd little noises in the dark. At night they're reminiscent of a young puppy, breathing, panting, the strange little sudden squeaks and whimpers. The wake-up cries, that aren't for any other reason than to say, "Hello! I'm awake!"
The slow development from an odd pink mewling thing into a little person. The eyes gradually focusing more. Shifts in its attention with its first faltering interactions with both you and its environment. Those odd early moments when something catches and hold its attention briefly.
The slow rediscovery of the world through someone who hasn't seen any of it before. Everything will be new again. A ball as an object of wonder, a new surface something to be explored, a tree, the ocean, the sky, all brand new for a new little person.
And this little person loves you, wants to be held by you. To them, you are the centre of its world, and it the new centre of yours. And despite all the problems and worries, the interruptions and sleeplessness, the frustration and confusion, you know at the core of your being that this little person is worth all of it and more.
You think you know it will be that way before you become a parent, but like all the things you try to prepare yourself for beforehand, the stress, the tiredness, you can't understand the reality of just how deeply it will affect you until it's happening.
It's only when it's happening, with the joy and wonder mixed with the hardship, that you can feel in the heart of your being how truly worth it it is.