Adding rows to grid on scrolldown

I have created a 3x3 Grid, this grid covers the entire screen.
I want it so that when the user scrolls down rows and columns in those rows are added into that Grid. So it should look like an image gallery.
How do I go about doing this?
Sorry if this is too vague, I’m just starting out.

Do you want the rows and columns empty or are there images / some kind of data that you want to be presented?

Yes, images. Like the search or explore page on Instagram wherein new images are loaded as the user keeps scrolling down.