We are honored to introduce the 4th Internationalconference on capacitive deionization and electrosorption, which will take place atBeijing, China, from May 20 to 23, 2019. The conference will be a good forum for CDI researchers to present the latest results, to draw inspiration and ideas, and to probe into the future development of CDI&E technologies. We are grateful for your continuous attention to the conference and welcome your attendance. We wish you have an unforgettable experience in Beijing, China.