Correction: An earlier version of this story gave the incorrect name for the pediatrician who started the What’s Up Doc program for teens. Her name is Marilyn McPherson-Corder. This version has been corrected.

Children from the District, Maryland and Virginia and about 400 volunteers gathered at the Show Place Arena for the 21st annual Thingamajig Invention Convention. (Hamil Harris/The Washington Post)

There were robots, drones and even a fake operating room at the Show Place Arena last week as more than 4,000 children and 400 volunteers participated in the YMCA of Metropolitan Washington’s annual Thingamajig Invention Convention.

Prince George’s County Executive Rushern L. Baker III (D) and other representatives from the public and private sectors came to Upper Marlboro for the 21st annual event, which brought together children ages 5 to 14 from the District, Maryland and Virginia.

“This is so great. This is not just a one-day event; they have been doing this all summer long,” Baker said. “It also makes sure that our children and children around here don’t lose any progress they made in school. So they are having fun, but they are also learning about math, science, engineering and technology.”

The arena was filled with exhibits, including a robotics and drone exhibition run by several groups affiliated with First (For Inspiration and Recognition of Science and Technology).

Chris Stephens, an aerospace engineer and commercial pilot from Upper Marlboro, attended the event with his son. They are part of a drone and robotics group from Greenbelt called Team Illusion. Stephens, who works for the National Transportation Safety Board, said that not only has his son learned about robotics and aviation, but “these kids are using programming languages.”

Sydney L. Foust, left, Samirah Stokes, Nneoma Nnakwu and Ikechukwu Ihejirika are part of the What’s Up Doc pre-med program. (Hamil Harris/The Washington Post)

Bryce Stephens, 11, seems to be following in his father’s footsteps. He described his drone, which had four propellers, as “pretty cool,” adding that he has “learned a lot of ways to program and to build.”

Don Brobst, a senior mentor with First, said, “STEM education is really the end thing right now, and robotics offers kids not only the ability to apply the scientific principles — they can actually build stuff.”

Janice Williams of the Metropolitan YMCA came up with the idea for the Thingamajig Invention Convention more than two decades ago.

“I know that there are children who come to Thingamajig who are excited about demonstrating their creativity in ways that they have not been able to do before,” Williams said. “We really need to allow our young people to be able to demonstrate their creativity out of the box and to solve problems and give them an opportunity to explore new areas.”

Three teenagers, Mya Hobbs, Roman Harden and Miracle Forbes, were all dressed in white lab coats and huddled around a life-size fake cadaver, on which they practiced removing organs with metal tongs. (The students also had several copies of the board game Operation.) The teens are part of “What’s Up Doc,” a pre-med club sponsored by the Prince George’s County Chapter of Links, an African American women’s volunteer service organization.

Geneva Mays, a charter member of the Prince George’s Links, said pediatrician Marilyn McPherson-Corder started the programs for students because “it is essential to give them opportunities. Maybe they won’t go into medicine, but at least they can understand the different parts of the body and how they perform.”

Angie Reese-Hawkins, president and chief executive of the YMCA of Metropolitan Washington, said that “Thingamajig epitomizes what the Y stands for, and it is all about making sure that youth remain connected, feel secure and can be creative. What is really important is STEM; it is the foundation for the economic prosperity of the future.”