Voronoi Cells

I have a question about Cycles Voronoi node. Is there a node tree that manages to create a material that shows that voronoi cells, but instead of painting then with different colors, just diferentiate the “borders” between then? Take this picture for example:

Forget about the little red dots. notice that all the cells are white. Instead of having diferent colors, like the voronoi node from cycles do, we see the different cells because the borders between then is black. Is there a way to achieve this with cycles nodes only, or we need to use OSL?

A couple of possible options

Option 1

Option 2 (adjust the colour ramp to adjust line thickness)

Option 2 uses an OSL script from https://blenderartists.org/forum/showthread.php?378763-Voronoi-cracks-glow&p=2969945&viewfull=1#post2969945


voronoi edges.blend (131 KB)

Wow, thanks a lot! I really didn’t believe it would be possible to achieve this whithout using OSL, but now I see it is actually simple :P! Thanks again, this will really be useful to me!