Rule of 7 in research. You can find out anything if you are willing to go seven levels. If the first source you ask doesn’t know， ask them who you should ask next， and so on down the line. If you are willing to go to the 7th source， you’ll almost always get your answer.

深度学习是一种机器学习形式，它使计算机能够从经验中学习，并通过概念层次来理解世界。