Most mainstream A.I. research today involves deep neural networks, which build on the larger field of machine learning. Machine learning techniques use calculus and statistics to make software we all use, like spam filters in email and Google search. Over the last 20 years, researchers began applying these techniques to a new idea called neural networks, a software structure meant to mimic the human brain. The general idea is to decentralize computing over thousands of little equations (the “neurons”), which take data, process it, and pass it onto another layer of thousands of little equations.