What are some of the greatest technological achievements?

Hi Su ^^

In my opinion, electricity is a greatest discovery in human history.

>>> In my opinion, electricity is one of the greatest discovery in human history.

 I\'m not sure who discovered electricity, but everyone, who lives this century, believes the importance of electricity.

>>> I\'m not sure who discovered electricity, but everyone, who lives this century, believes in  the importance of electricity.
 

Almost every part of our life, we use electrical devices. 

>>> correct

 Not only like vital sphere like home, school, firm, hospital and also leisure facilities….

>>>  Not only like vital sphere like home, school, firm, hospitals and also leisure facilities.

I can not even imagine what will happen when we lose this convenience of modern age.

>>> correct

 Last time, I was surfing on the Internet, when all of a sudden the lights went out.

>>> correct

 I was horrified by this situation and tried to solve this problem.

>>> correct

 It was blackout and literally, everything was totally black.

>>> correct

 Fortunately, in that time, my cell phone worked and it was just for a short time,

>>> Fortunately during that time my cell phone worked but just for a short period of time.

 but if the stage would be long lasting, then it should be a terrifying problem.

>>> But if it would last longer, then it would be a terrifying experience.