The letter fundamentally provides a comprehensive overview on the articles published in the Journal IEEJ Transactions on Electrical and Electronic Engineering on multi‐input multi‐output (MIMO) systems. All the methods, criteria, metrics and requirements are essentially taken into consideration. Finally, an outline‐based figure is given, listing all the references investigated in the letter. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.