Millennials Ð those born between 1981 and 1997 Ð make up about 40% of the workforce in the United States. These workers bring a unique outlook to their jobs, and may also pose unique challenges. Taking time to customize the onboarding process for millennial employees helps promote employee retention and ensures that millennials are properly integrated into the workplace. Customizing the onboarding process for millennial employees benefits the employee and the workplace.