Millennials are the group that follows Gen Xers and there appears to be no exact dates as far as I can tell as to exactly when this generation starts and ends, but depending on who you ask people in this group were born somewhere around the early 1980s to somewhere around 1995.
That puts this group between the age of 19 and 34 and the best I can tell there are somewhere around 78 million of them out there, compared to the 76 million baby boomers, and these millenials have an annual buying power bordering on $200 billion.