&gt; In practice, neural networks use only two or three layers...<p>The famous AlexNet [1] that blew away the ImageNet competition in 2012 contained 8 layers; more recent networks have even more.<p>[1] <a href="http:&#x2F;&#x2F;www.cs.toronto.edu&#x2F;~fritz&#x2F;absps&#x2F;imagenet.pdf" rel="nofollow">http:&#x2F;&#x2F;www.cs.toronto.edu&#x2F;~fritz&#x2F;absps&#x2F;imagenet.pdf</a>