Step 1: You Will Need
1. A computer with the following specifications: http://support.google.com/sketchup/bin/answer.py?hl=en&answer=36208
2. Sketchup installed on the above computer. If you don't know how to install software then maybe try an easier instructable. If you don't have Sketchup installed then look here: http://www.sketchup.com/intl/en/download/
3. 30 minutes to 1 and a half hours depending on you previous knowledge of Sketchup and how quickly you work. (The first time took me about 2 hours to work out where I was going to start and the best way to construct it).
4. A mouse. Trust me - invaluable.
Step 2: Open Sketchup
Step 3: Starting the Model
Firstly, once the 'creation window' has opened, click on the Rectangle/Square tool.
Click on the Origin with the rectangle tool selected.
Use the rectangle tool to create a square 50mm by 50mm.
Step 4: Construct the 'Wireframe'
Use the Rectangle tool to go over the 40mm by 40mm square traced by the guides.
Delete the internal square and then use the extrude tool to raise the remaining shape up 5mm.
Outline each 'leg' (as seen in the picture) and extrude each one up 40 mm.
Use the line tool to connect the legs at the top. You will probably have to delete some extra faces that are automatically created so that you just have the 'wire frame'.
Extrude the top parts up 5mm - see image.
Delete unnecessary lines around latest extruded [arts and your model should now look like the final image for this step.
Step 5: Construct the Internal Cube
Use the Rectangle tool to go over the 25mm by 25mm square created by the guides, then delete the guides.
Extrude the square up 37.5mm.
Extrude the Bottom of the now rectangular prism up 12.5mm. You should now have a 25x25x25mm cube.
Step 6: Construct Ineternal 'Wireframe'
Delete the extra faces of the internal cube to create a 'wire frame' outline.
Finish the internal wire frame using your preferred method to make each 'leg' 3d. See image for finished internal wire frame.
Step 7: Connect the Cubes and Finish Your Tesseract
Firstly, on he top 'face' of the internal cube, outline the legs - see image.
Use the line tool to connect the outer corner of the internal cube to the corresponding outer corner of the outer cube. Do the same for internal corners.
Finish the connection as shown in the image.
Repeat above steps for bottom of internal cube.