Render multiple Layers, how to mix/combine them, it's not working here I am startup up with Blender and through an internet course I created a scene, which are heavy to render on my pc.
So I started to investigate Render Layers, ideal for my situation I thought, I can render each Layer at a time, also on different computers and eventually combine al rendered images together, to created a final Rendered masterpiece.
I am figured out that I have to set Transparency on, on all images.
So I did.
And for the background (World), which will be displayed on the back, with everything in front of it, I figured Transparency is not needed, so I rendered an empty Layer with the Environment setting on.
I now have 3 images to start with, more Layers will be rendered in a later stadium.
So I find out that I have to use the Node Editor with a box called Alpha Over to combine them, so I did, see screendump picture.

But the problem is, my combined end result is not showing anywhere.
What am I doing wrong, is my approach not right, I'm kinda stuck here.
Help would be much appreciated!
Regards
Martijn.
It worked. I rendered 3 layers and in the node editor I checked use nodes and backlog. 
And then using alpha over I combined them and the result was shown :