The 4th edition of Work in the 21st Century: An Introduction to I-O Psychology retains the accessibility of the previous editions while incorporating the latest research findings, and updated organizational applications of the principles of I-O psychology. The scientist-practitioner model continues to be used as the philosophical cornerstone of the textbook. The writing continues to be topical, readable, and interesting. Furthermore the text includes additional consideration of technological change and the concomitant change in the reality of work, as well as keeps and reinforces the systems approach whenever possible, stressing the interplay among different I-O psychology variables and constructs. Additional themes that are discussed throughout the text are: work becoming increasingly cross-cultural and multinational; workforce becoming more diverse; work teams and becoming more common; work-life balance is an important topic for employees/employers; among many others. New themes topics and themes include: Evidence-Based I-O Psychology; Social Responsibility in Organizations ; Humanitarian Work Psychology; Job Engagement; Learner Engagement; Technology-Delivered Training and Instruction; Social Networking & The Workplace; Genetics, the Big Five, and Work.