Coffee behemoth Starbucks (SBUX) closed all of its 8,000-plus U.S. stores for four hours on Tuesday afternoon so its 175,000 employees could participate in company-wide racial-bias training.

“I don’t know of another company in the history of American business that’s done anything remotely like this,” executive chairman Howard Schultz said.

Closing all U.S. stores comes at a price. Bloomberg estimates it could result in $16.7 million in lost sales, which compares to $22.4 billion in revenues the company had in fiscal 2017. Starbucks will also be paying all employees participating in the training.

“[It’s] quite expensive,” Schultz said. “We’re a public company and we’ve had certain shareholders call and say, ‘How much is this going to cost and how do you justify this?’… My answer to them was, ‘We don’t view it as on an expense. We view it as an investment in our people and the longterm culture and values of Starbucks.’”

Some customers took to Twitter to share their frustration at not having access to their afternoon caffeine fix, while others watched in amusement as people attempted to enter the closed locations.

Others praised the company.

The training comes in the aftermath of the arrest of two black men, Donte Robinson and Rashon Nelson, in a Philadelphia store in early April. They were waiting for a friend without purchasing anything when a manager called the police resulting in their arrests.

Right away, Starbucks’s leadership went on an apology tour and called the situation “reprehensible.”

The manager whose phone call resulted in the arrests has since left the company. Starbucks settled with Robinson and Nelson for an undisclosed sum.

Following the Philadelphia incident, Starbucks also announced that it would close its stores for racial-bias training. The company also altered its bathroom policy, opening the stores to nonpaying customers.

A Venti-size training session

Yahoo Finance got a glimpse at the training materials being used in stores on Tuesday during the four-hour long session. These materials consist of a 68-page guidebook that resembles a newspaper and an iPad for each group and a private notebook for each employee.

The average store consists of roughly 20 employees. Each store “family” broke into groups of three to five people.

As they went through the guidebook, they were given cues to watch a specific video on the iPad, which was then followed by exercises in the personal notebook and group conversations.

The “ground rules” were “listen respectfully” and “speak your truth and honor other people’s truth.” If conversations got “off track,” they were encouraged to pause and restart.

“Conversations about race can induce a feeling that experts call ‘racial anxiety,’ and when we’re anxious, we can’t always think clearly,” Starbucks president of U.S. retail Rossann Williams says in one video.

There was also a 1-800 number for employees to call and navigate through challenging moments when they needed additional help.

In one exercise, employees were asked to pair up and quickly find the ways they are different from one another. In another instance, employees were asked to reflect in their notebooks “the first time you…”

• “… noticed your racial identity.”

• “… noticed how your race affected your beauty standards.”

• “…felt your accent impacted people’s perception of your intelligence or competence.”

Carla Ruffin, a regional director in the New York-Metro region and a black woman, told Yahoo Finance that she found the training to be “really profound.”

“I think what we did today we need to embed in our training and in our daily culture. I call it ‘saying things out loud,'” Ruffin said. “We need to just have that conversation and say it out loud. I think it brings people together and it helps keep those biases at bay.”

For Ruffin, the arrests in the Philadelphia store had many layers.

“I immediately understood that there had to be more behind it than just what I saw on film. I didn’t immediately think there were suspects or people with ill intention. I think it was caused by the exact thing I first said is that we don’t put biases out there and talk about them and therefore people are acting within those biases.”

As a mother of a son who just graduated from college, she also felt disappointment and concern seeing the two black men arrested. She views this as a moment to start a more extended conversation.

“And then there was also that I wished it didn’t happen, but I have this faith knowing who Howard [Schultz] is and knowing why I’m part of this company that it’s this opportunity for us to make a difference.”

The training also brought in some familiar names, including hip-hop artist and activist Common. Award-winning documentary filmmaker Stanley Nelson also produced a film entitled “You’re Welcome” as part of the training.

Nelson’s film highlighted testimony of how people of color, many of them young, feel in public spaces, while a white man in the film says when he leaves his house he walks out a “free man.”

“Me, being a man of color, I migrated to the United States from Guyana, from South America, and I ran right into racism in 1993 just walking down the street,” said Les Fable, a district manager in Brooklyn, told Yahoo Finance afterward. “Some of the videos that showed some of the young men speaking to the extent of walking into a store and being followed, or people thinking that you’re going to steal stuff, I experienced that. It was a little concerning that those things are going on today.”

Fable referred to Tuesday’s training as a more of a “discovery” for employees to listen and have a “transparent conversation.”

“What happened in Philly, no question, we could have done better. There were so many other approaches that could have happened without leading to calling the officers. I think it’s more so the disconnect, not the with the company, but more so with ourselves. I think if we’re not challenging ourselves we’re going to continue to point a finger and blame other people.”

A step, not a solution

The curriculum, prepared by SYPartners and the Perception Institute, involved experts, including Bryan Stevenson, founder and executive director of the Equal Justice Initiative; Sherrilyn Ifill, president and director-counsel of the NAACP Legal Defense and Education Fund; and Heather McGhee, president of Demos, and many others.

“There’s no expectation on anyone’s part that a four-hour block of training is going to comprehensively solve the issues of racial bias, or inequities, or discrimination,” Schultz said. “However, it’s critically important to start this conversation.”

From now on, the training will be part of the onboarding process for new hires. For the next year, Starbucks employees will be given one topic per month to discuss as part of this ongoing training. Stores will not close for those monthly discussions.

The training will be available for other companies and organizations.

“The promise of America will not be achieved if it is only available to those that have the right color of skin or have the right zip code and we must provide opportunity and aspiration to every single person who is American, and we must see that through the lens of humanity,” Schultz said. “And I think this exercise is the beginning of that for Starbucks. And if it can, in any way, be a catalyst for companies and other organizations and for the country that would be a wonderful thing.”

Julia La Roche is a finance reporter at Yahoo Finance. Follow her on Twitter.

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