The worlds greatest invention?

Well basiclly I got asked this question the other day in the street and given a peice of paper to write a long paragraph, so they said what the worlds greatest invention and why do you think it deserves to be the greatest invention ?!
So people what do...

you guys think and why it deserves to. X

I think the greatest invention is the wheel, imagine life without transportation
Others are
Electricity, which led to many great inventions like the light bulb internet.
The printing press, which contributed to literacy.
Written Language, which provided records.

if I was a girl id say a vibrator... why its the best would speak 4 itself lol

I'd say the lightbulb
because it's prevented a lot of accidents ^^

I think the most common answer for this is the printing press. It allowed for books / the Bible / other things (ie. pamphlets, early newspapers, political documents) to be published and disseminated much quicker than hand-printing.

The printing press did more to further the advancement of humankind than any other single invention in history. The rapid dissemination of information caused an explosion of ingenuity and creativity that has not been seen since.

--the cell phone