Electronic ink is a new technology that allows for reusable and rewritable paper-like displays. It uses microcapsules filled with charged pigment particles that can be manipulated by electric fields to appear black or white. When applied to paper pages, it allows books to function like e-readers with updatable content. Two main approaches are E Ink's use of electrophoresis to move particles in microcapsules, and Xerox's use of rotating black and white balls in microcapsules. Electronic ink provides benefits over traditional paper like dynamic updates and a whole library in one reusable book.