Here is an image of the entire Update 4 Research tree.

I pasted together screen shots from Sandbox mode and Sailor Difficulty, so Research costs may vary.

This image is HUGE. To see the image clearly you will have to:

1. Click image below to Zoom \
2. Right-click the zoomed image and "save image as" and click "Save" to get the full size 12,387 x 1,961 JPG Image. \
3. Then open in your favorite image viewer.