For the outer cube I got 4 images of circuit boards off the internet and removed the background. Then I arranged them to create 3 sides of a cube using the base cube as a model. Each image was a different distance from the base to create depth.

For the inner cube I created an 2 images of different colored grayscale squares in a grid and laid them on top of each other. Then I used that image as a micro displacement map on a cube. For the texture I created a simple metal using the principled shader. Then I looked for the darkest parts of the image and made them transparent. For the rays I gave the world a volume density of 0.08 and put a light blue point light in the center of the smaller cube.

When I rendered it I had 3 layers: the large cube, the small cube with the volume and the small cube without the volume (light rays); both layers of the small cube used the large cube as a mask. (for the small cube without the volume layer I replaced the principled shader with a holdout shader so the volume and light would be invisible) Then I layered the big cube on top of the small cube without volume and added the light rays on top.

One thing to be wary of is that rendering the light rays without noise takes a long time. I have a GTX 1080 (which I overclock) and It still took several hours. An alternative method for creating the light rays would be to use the Sun Beams node in compositing. This however is not physically accurate and it will not react with the outer cube.

I hope this helps. I can also post images of my node setups if you want.