Considering the $350 billion combined spending power of Millennials and Gen Z, brands have made it a priority to reach them, motivate them, and inspire loyalty among them.

But what's truly motivating these younger audiences? How do they differ? And what strategies and tactics can today's marketers use to inspire the enduring loyalty of Millennials and Gen Z consumers?

To find out, I recently hosted a panel at Nerd 100 with prominent marketers and researchers who excel at understanding, engaging, and bridging these two generations of customers. Here are some of the things experts from Facebook, Airbnb, Lyft, Ellevest, and InterQ Research had to say.

1. In Millennial and Gen Z marketing, immediacy matters

One of the dominant themes from the panel was the idea that the window for successful engagement is extremely narrow, so marketers really need to be in tune with cultural trends and relevant in the right moments.

These younger audiences—Millennials, who are 23-38 years old, and GenZ, who are 7-22 years—are true digital natives and they consume vast amounts of data each day. In fact, the average attention span for Millennials is just 12 seconds. It's an even shorter eight seconds for Gen Z audiences; moreover, Gen Z consumers often consume content on up to five screens at once, compared with Millennials' three screens.

That's one of the reasons Facebook's Jasmine Clennon, advertising insights marketing strategist, attributes to the rising popularity of Stories. The 24-hour time limit for this popular vanishing-content format has unique appeal for younger audiences that crave authentic, immediate experiences.

To inspire engagement, brands should "play more," she suggested, emphasizing that younger consumers enjoy stickers, emojis, and playful photos and videos that allow them to express themselves around the brands they use and enjoy.

The idea, of course, isn't to deliver an endless cascade of meaningless content; rather, it's to deliver a steady flow of meaningful content to an audience that craves immediacy.

2. Build a community

Time and again, the panel's conversation returned to the idea that younger consumers see the world in entirely different ways and have different priorities than prior generations.

"So many young people today don't even want to own a car," observed Dave Kim, consumer product marketing lead for Lyft. "They no longer see it as a symbol of freedom, or a sign of their independence. Instead, they want an authentic experience with their Lyft driver and a connection to the community they're traveling through."

Tony Högqvist, executive creative director at Airbnb, agreed. He pointed out that Airbnb has expanded its business model to include passions and experiences in response to younger customers who expect more than a clean, safe, affordable room. He also noted that younger customers require "connected sources of social truth" in the journey to brand loyalty, meaning they build trust over time, synthesizing insights from family, friends, and influencers in and around the communities they visit.