11. A cross-section of a tortoise skeleton
12. A small section of the Golden Gate Bridge cable
13. A pine cone split in half
14. The inside of a bowling ball
15. The inside of the camera lens
16. An underwater power cable
17. Adding machines like this one were used by bookkeepers until the 1970s
18. The inside of a frag grenade
19. A rattlesnake’s rattle
20. A cross-section of a gun
