Animation: how can I make an element appear gradually without moving?

Hi! So I have the idea in my head but I can’t find the right kind of animation. It’s quite simple so I think there should be a way.
I want the element to appear when scrolled into view and I want it to gradually grow from top to bottom without the whole element moving around. Basically, I want it to be invisible first and then gradually get visible starting from the top. How can I do it?