As a kid growing up in Medford, Michael Bloomberg would spend his Saturdays at the Museum of Science. From when he was just eight years old, Bloomberg, 74, would take a bus from West Medford to Sullivan Square and then a train to Lechmere in order to get to the Museum.

“I looked forward to that trip all week long,” he said.

Standing in front of the Museum on Tuesday, Bloomberg said that he “never in a million years” would have thought he’d be back here to name a part of the museum after his parents. Thanks to his $50 million donation, the Museum of Science has renamed its Education Division as the William and Charlotte Bloomberg Science Education Center.

The Museum of Science and Bloomberg Philanthropies, founded by the entrepreneur and three-term New York City mayor, announced the donation with a ceremony to unveil the new signage on the front of the Museum building.

The donation is the largest in the Museum’s 186-year history, but it’s not Bloomberg’s first contribution to what he has called his “first teacher.” Bloomberg has donated to the museum three previous times: One donation supported the 2011 renovation of the Charles Hayden Planetarium; the second supported access and internship programs; and the third, a planning grant, enabled the Museum to redesign exhibition and programming spaces.

"This museum really changed the course of my life," Bloomberg said. "Everyone remembers the first teacher to have an impact on their ways of thinking and understanding the world, and for me that teacher really was the Boston Museum of Science."

Bloomberg has donated to other local institutions as well, showing that he never forgot his hometown. He helped fund the Mother’s Walk on the Rose Kennedy Greenway and gave $32 million to Harvard—where he attended business school—to help fund an executive education program for municipal leaders.

This recent gift will support the creation of new computer science and food science initiatives and continue to bolster the current education engineering and STEM programs. To Bloomberg, it’s about showing that STEM education in America is worth funding.

“We live in the most wonderful country in the world, we just have to make sure that all of the kids who live in this country have the opportunities that I did,” Bloomberg said.

Museum of Science President and Director Ioannis Miaoulis echoed the sentiment that Bloomberg’s gift will truly help all children advance in their science education.

“Mike’s generous act is a testament to his belief in education and his passion to make the world a better place,” Miaoulis said. “Mike has given Boston, Cambridge, the Commonwealth of Massachusetts and the world a tremendous gift.”

Boston Mayor Marty Walsh and Cambridge Mayor Denise Simmons (the Museum spans the two cities) and Massachusetts Gov. Charlie Baker were in attendance as well to talk about their own experiences being transformed by the magic of the Museum and to thank Bloomberg for his gift.

“Your seminal gift here today is just one more example of your ability to think deeply about what really matters to you and what you believe matters to kids in this country,” Baker said to Bloomberg. “On behalf of the people in Massachusetts, I just want to say how pleased and honored we are to be able to consider you a son of Massachusetts, despite the fact that you’ve been somewhere else for a few years. But I have to tell you—anytime we can take $50 million from New York, I’m all for it.”