A decade later, as an early employee at Google, I became reacquainted with machine learning when the company was still just a startup. In 2001 we used a simpler version of machine learning, statistical ML, to detect spam and suggest better spellings for people’s web searches. But it would be another decade before we had enough computing power to revive a more computationally-intensive machine learning approach called deep learning. Deep learning uses neural networks with multiple layers (thus the “deep”), so it can learn not just simple statistical patterns, but can learn subtler patterns of patterns — such as what’s in an image or what word was spoken in some audio. One of our first publications in 2012 was on a system that could find patterns among millions of frames from YouTube videos. That meant, of course, that it learned to recognize cats.