At Google headquarters, employees are offered hundreds of free classes. But one of the most popular is called “S.I.Y” or “Search Inside Yourself,” taught by engineer and Google employee Chade-Meng Tan, according to a recent article in The New York Times.

Tan worked with nine experts to put the course together and the class has three steps – attention training; self-knowledge and self-mastery; and the creation of useful mental habits, according to the NY Times report.

So far, more than 1,000 Google employees have taken the course, and there is a waiting list of 30 people for the next time its offered, the report stated. Each class takes 60 people, and it runs for seven weeks, four times per year.

“I’m definitely much more resilient as a leader,” Richard Fernandez, director of executive development and a psychologist by training told the newspaper about taking the course. “I listen more carefully and with less reactivity in high-stakes meetings. I work with a lot of senior executives who can be very demanding, but that doesn’t faze me anymore. It’s almost an emotional and mental bank account. I’ve now got much more of a buffer there.”

Additionally, in anonymous reviews, Tan told The New York Times that on average, participants rate the course approximately 4.75 out of a possible 5.

“Awareness is spread almost entirely by word-of-mouth by alumni, and that alone already created more demand than we can currently serve,” Tan told the newspaper.

Tan’s first book, “Search Inside Yourself: The Unexpected Path to Achieving Success and Happiness (and World Peace)”, is available now.