Millennials, accounting for 24% of the U.S. population, exhibit significant diversity and variations in lifestyle, with younger segments often living at home or in shared housing, and older segments being more established. They are also major consumers with a preference for authentic communication and a strong inclination towards discount shopping, heavily relying on their smartphones for information and entertainment. Key takeaways for marketers include the need for targeted segmentation, mobile engagement, and support of social issues to resonate with this generation.