John Mack, the former chairman and chief executive of Morgan Stanley (NYSE:MS) has a new prominent spot in the business world. He was just hired as senior adviser by KKR & Co. L.P. (NYSE:KKR), a firm that specializes in private equities.

In 2010, Mack handed over his chief executive role to James Gorman and less than a year ago, he left his chairman role at Morgan Stanley. Since then, he’s been a valuable part-time adviser for Stanley and he will continue on that role even with his new career. He’s also in the works of writing a book and will take on a role as a director at Rev Worldwide.

One of the co-founders of KKR explained why they offered Mack a key position, “(he is) great leader who we believe will add enormous value to KKR’s investors, partners and our portfolio. He will help make us smarter investors and strengthen our firm”

John Mack released a statement as well, “The volatile economic environment has created a demand for both capital and operational expertise and I am proud to join a team that offers both of those things and so many other resources that can help companies achieve their goals and investors meet or exceed their needs”

KKR(Kohlberg Kravis Roberts) oversees and sometimes works as a sponsor for private equity funds. It was also one of the founding companies for buyout leverages.  The company was launched in 1976 by Jeremy Kohlberg Jr, George R. Roberts, and Henry Kravis.

This sounds like an exciting new venture for him and KKR. Mack will be able to apply his long-term experience(he joined the Morgan Stanley team back in 1972) to share his expertise and provide future insight. In the business industry, the longer you’ve worked for a key company, the more valuable of an asset you will be for the next company.