Mystery of Ancient Pyramids | How were they really built?

You must have seen several pictures of Egyptian Pyramids. We all agree that they are really beautiful - but have you ever thought about who built them, and how were they built? Because they were built at a time when there was no machinery, no infrastructure, no technology, nothing. So what is the story behind these giant structures that weigh 6 million tons? Why are they shaped like that? How were the stones transported?