Inventions that changed the world!

20 inventions that changed the world:

1 wheel
2 printing press
3 paper 
4 nails
5 compass
6 electricity
7 light bulbs
8 penicillin
9 engine
10 concrete
11 semiconductors 
12 batteries
13 telephone
14 refrigerator
15 car
16 airplane
17 internet
18 web
19 computers
20 smartphone