Overlaying Images + C#

Question

Hey,

Im trying to think of a simple way to overlay an image within a picture box... i basically have a small tileset editor and i want to overlay images over to show the collision detection, but no matter how much i try i cant find any information on merging images with alpha channels...

Any information or links would be great, both are in PNG format, and the bottom layer (the tileset image) would have small transparent bits, the 2nd layer would be a 40% transparent red colour in various shapes...