Side nav menu with accordion sub-items

558fe5180e0e8fc922d31c23ef84d240

I've searched, but can't even find what to call this. Any links or code would help a ton. I want 8 main items to appear from a side-menu with 4 sub-items branching out to their right when clicked. As any sub-item is clicked, I'd like for 4 items below that to appear in an accordion-style fashion. The entire thing should never get any larger than 8x2.

Does this make sense? What am I looking for here? Thanks for any help you're able to provide.