Over the past few years, co-working has made headlines for turning the workplace on its head. In recent weeks, its lesser known counterpart—co-living—has gotten its first big media rollout. These overlapping trends represent a cultural shift away from traditional work and home environments. What is fueling their growth? Generational change. These community-oriented, structured, and shared concepts appeal to the Millennial mindset. While co-working and co-living aren’t without their drawbacks, they will likely be around for the long haul as Millennials continue to put a new spin on the young professional lifestyle.

Over the past decade, co-working and co-living spaces have gone from Silicon Valley “hacker mansions” to full-fledged business enterprises. According to the Commercial Real Estate Development Association, there were 781 co-working spaces in the United States in 2013—up from just one in 2005. And these numbers have continued to grow. WeWork, for example, doubled in size from 2014 to 2015 to 98 locations in 28 cities around the globe. Boston-based Workbar has expanded to 12 locations since its founding in 2009.

Adam Neumann, co-founder and chief executive officer of WeWork, speaks during the TechCrunch Disrupt NYC 2015 conference in New York, U.S., on Tuesday, May 5, 2015. (Credit: Michael Nagle/Bloomberg)

Co-living has also gained momentum. For Millennials, living with friends and family is the new normal—and now, companies are explicitly organizing housing options around the idea of group living. Common, for example, currently has three co-living locations in New York City. And WeWork has launched its own co-living operation, WeLive.

Both co-working and co-living represent a profound shift away from how Americans have always operated. Co-working startups, for example, lease office buildings and sublet the space to teleworking professionals, independent contractors, and small companies who rent or pay a membership fee to work in a shared space. These spaces are designed to maximize interaction, whether by way of networking events or monthly pancake breakfasts. Co-working spaces also provide Silicon Valley perks—including yoga classes, monthly hair blowouts, and even free beer on tap.

Co-living is simply an extension of this same trend. Co-living startups lease apartment buildings and rent out bedrooms to individuals—often for much less than a one-bedroom apartment. What’s the catch? Residents must share bathrooms, kitchens, and common areas. (Think “dorms for adults.”) Like their co-working counterparts, co-living companies offer a wide range of conveniences, including laundry services, massages, and housecleaning. Co-living also entails a wide range of scheduled events for residents.

Generational change is fueling the rise of co-working and co-living arrangements. These spaces tap into multiple segments of the Millennial mindset.

Most importantly, the co-working/co-living movement reflects the Millennial desire for community. Unlike young Boomers, who considered living alone and having the corner office the ultimate goal, Millennials would rather live and work together. Before co-working spaces, work-at-home professionals and independent contractors would simply meet up when they needed to collaborate on a project. Today’s startups have formalized this process and have added opportunities to socialize and collaborate with other groups.

Co-living spaces have a similar mission. Whether its group dinners or book clubs, these arrangements are crafted to cure the isolation often felt in big cities. Millennials in particular crave community and don’t mind relying on others for company. But many are putting off the relationships that would fill these needs—namely, marriage and family. (This tension explains the expansive online literature on lonely young people.)

Millennials like the structure and safety these offerings provide. In many ways, co-living and co-working environments operate in loco parentis. Co-working startups are responsible for making sure the printer works and the office stays tidy while workers concentrate on the task at hand. And if a startup fails, employees can snag a job with another company in the same building. For Gen Xers and Boomers, the thrill of startup life was mostly tied to the risk of striking it out on your own. Millennials, however, want a safety net to catch them if all goes wrong. Co-living eases the burden of living alone. These apartments have a hierarchy of authority figures who operate as residential advisors—intervening when conflict arises.

Millennials don’t mind sharing space with (or being dependent on) others. For this generation, there’s no reason to own a car when there’s Uber. Or buy a dress for a work gala when there’s Rent the Runway. In that same vein, why pay for your own kitchen when it’s less expensive to share? Of course, it takes trust for this setup to work. Millennials have been the recipients of special care since birth—and trust others to look out for their best interests. This runs completely against the instincts of Xers who didn’t have anyone looking out for them when they were growing up.

Millennials also have a more blended definition of work-life balance. They want to prove themselves in the office, which often means going above and beyond the call of duty. This is particularly true for those in the startup world, where sparks of inspiration may hit at 3 a.m. Co-living and co-working spaces promise that someone will always be around to help brainstorm for new ideas. It also means that when every coffee shop is closed, there will be complimentary caffeine within walking distance.

To be sure, there can be such a thing as too much co-everything. There are times both at work and at home when privacy is needed—which is why co-working startup Alley offers private phone booths. Additionally, these environments require strict rules to keep the peace. This is hardly a problem for rule-abiding Millennials, but may not fly for older generations who don’t want to be told what to do.

In the years ahead, these arrangements will likely continue to grow and expand. For Millennials, co-working and co-living are a slam dunk. As Millennials age and their needs change, these offerings will likely evolve to meet them. Millennials’ extreme desire for togetherness is already bringing back “live-work-play” communities first popularized by urban-loving Xers. Only time will tell what sort of co-situations will become the norm in decades to come.