I hesitate to post a picture as I'd have to thieve it out of a competitor's brochur <grin>
Image the corner of a glass display case. We have three pieces of lumber about 2X2 in coming together in the corner, one each on the X, Y and Z axes. When fitted together we see the sticks joining with 45 degree miters in each direction... essentially each stick point touches the outer corner of the case. Inside there are mixtures of dovetails and a little mortise/tennon that hold the thing together.
I posted this for curiosity. As I say, I'd like to make a joint just to show off to friends... at least until I need to build a display case.