How do leaves grow?

Today, i've been sitting outside and admiring leaves. And wondering how they grow.

Here i share the leaves i observed, so you can admire and wonder, too. I encourage you to click the images to open them separately and see the details.

Where do the cells split? What is the algorithm behind it? Is it based on very simple rules? How does genetic information and the tree it's in translate into these wonders?

There are so many! Little natural solar panels. They are incredible.

It seems that the leaves keep their basic structure as they grow. I don't know anything else

And i found a time lapse of little oak growing on youtube (be careful, it's addictive!)