Capacitive Deionization (CDI) is a fast-growing technology which inherently reverses the age-old philosophy for water purification. While traditional methods separate the water from the contaminants, CDI selectively plucks out contaminants from the water, hence being very power and water efficient in operation. CDI, which is a purely electrostatic water purification method, has the unique ability to store energy while cleaning water, making it the only technology to truly address the energy-water nexus, and ability to bring about a paradigm change to the future of water treatment.