There are many inventions that have causde great changes in the word.there's a short introduction.for example,the digital camera which was invented by Steven J.Sasson in 1975 mke it convenient for all of us to take photos.Not only the cameramen but also the ordinary people can use the digital cameras easily.What's more,the photos taken by digital cameras can be kept in your computers.Whenever you want,you can retouch it.