As a generational expert with over 25 years in the field, Alexis Abramson has heard about all there is to hear from brands trying to appeal to various age groups. From baby boomers to Generations X, Y and Z—pick your group, and she's researched them, written about them and (probably) lectured brands on how to attract them, too. In recent years, a good many of those brands have had their sights set on the generation born between 1981 and 1996: millennials, aged 23-38 today. That's because at 83.1 million, a full quarter of the U.S. population, millennials are now the largest single consumer group out there. Simply put, few companies can afford not to court them.