Assembly co-founder and CEO Martin Cass likes to tell the story about the agency's humble beginnings just four years ago. Cass, Michael Nicholas (now chief entrepreneur in residence for MDC Media Partners) and Michael Day (now MDC Media's chief financial officer) crashed at a sister MDC agency, working at tables bought hastily at Walmart and, ahem, borrowing Wi-Fi from the coffee shop downstairs. And this was after some initial tumult, as the agency began as a mishmash: Parent MDC Partners merged RJ Palmer and TargetCast to form Assembly in 2014, and also rolled two other MDC media companies, Doner Media and Integrated Media Solutions, into the group.

"You want chaos? You try to do four mergers in a year," says Cass.

But living up to its name, the agency has fit the pieces together. In 2017, Assembly says, it saw a 12 percent year-over-year increase in revenue and scored more than 10 new clients, including Transamerica and Belkin, as well as the consolidated Boehringer Ingelheim account, all totaling $500 million in new billings.

Despite the great year, Cass keeps his outlook measured.

"Sometimes it's sunny and sometimes it's raining, but the umbrella isn't broken yet—that philosophy is very much my philosophy," Cass says. "In this industry, you're going to take some knocks and you're going to get some good times, but as long as you keep an even keel between those two places, you're going to be OK."

Cass says his team members, numbering nearly 500 across New York, Detroit and Los Angeles, are "big agency refugees"—people who want to do things a little differently and do the kind of work they believe in. And although it's owned by a holding company, Assembly isn't overly concerned about huge growth; it's interested in working with clients that want more than cheaper prices, Cass says.

Starting out, "we didn't have a number goal—that was never our objective," he says. "We wanted to work with the smartest, most progressive clients in the world." Cass says its clients, which include E-Trade, 21st Century Fox and FX Network, fit that mold.

In addition to the work produced, many of those clients may be drawn to Assembly because it works with AdFin to give clients access to their programmatic and digital transaction data. It's an effort to bring transparency cred to wary clients who want to know where their money is going. Assembly formalized the relationship with the digital provider in 2017, and Cass says some clients say it's enough just knowing the offer is on the table.

"I've been intrigued watching other people talk about their transparency story. If you mark your own homework, it's pretty easy," says Cass. "Think of it as an insurance policy: You don't know you need it until something goes wrong."