This document is the preface to a book titled "Emerging Technologies of the 21st Century" edited by Ajit Kumar Roy. The preface provides background on the global technology revolution and the potential for emerging technologies like information technology, biotechnology, nanotechnology, and materials technology to transform many aspects of life. The book contains 42 chapters organized into 6 sections covering topics like biotechnology, nanotechnology, expert systems, applied technologies, databases/modeling/analytics, and IPR/social issues. The preface expresses the editor's hope that the compilation of expert contributions will be useful for understanding the important role of new technologies and software tools in 21st century society.