How to create a material that is part solid, part transparent wireframe? For a 3D rendering of an organ, I would like to make part of it a transparent wireframe so the contents become visible (similar to this image, only I would like to have a much smaller area as the transparent wireframe). Could anyone point me to a tutorial, our explain me a bit how to approach this? Thanks!
In Blender Internal render engine, you can use Freestyle. To enable freestyle - Go to the render panel and click freestyle - 

Then go to edit mode, select the edges that you want to render and press "Crtl+E"
and click "mark freestyle edge".


Then go to "Render Layers", click on the Line set that should be automaticly created and click only on "edge mark"


Then on the tab "freestyle line style", you have options for the lines.

Then you can click on render.