The Brooklyn Children’s Museum may be 117 years old, but it is having its first growth spurt.

On Oct. 15, the institution will open an annex in Brooklyn Bridge Park — its first expansion since opening its Crown Heights flagship in 1899.

Spark, located in the luxury residential development One John Street in DUMBO, is a new art and play space designed for ages 6 months to 6 years that expands and builds upon the museum’s early childhood programs and classes.

The annex features an outpost of the museum’s signature early-childhood play space Brooklyn Block Lab exhibit, which uses building blocks to develop social and cognitive skills. As weather permits, the lab will be held outside in Brooklyn Bridge Park.

The space also has an art studio, soft crawl space for little ones and a hands-on area called the Discovery Den, which features science specimens and cultural artifacts from the museum’s collection.

“The opening of Spark represents an exciting moment in the museum’s 117-year history,” Stephanie Wilchfort, museum president and CEO, said in a statement. “Forever committed to serving the families of Brooklyn, Brooklyn Children’s Museum will be able to reach tens of thousands of more children and caregivers.”

Spark is also hosting semesterlong classes in areas such as storytelling, art and music (tuition is $300), as well as birthday parties.

Afternoon drop-in play hours are available Tuesday through Sunday with limited capacity, so advance reservations for hourlong play slots are recommended.