As you drive by buildings at NASA's Johnson Space Center (JSC), did you ever stop to wonder what's behind some of the doors? We did too, so we created "What's Behind this Door?" series. These will be 2- 3-minute video series targeted for both JSC employees and social media audiences. The series gives a behind-the-scenes look and explores behind different doors and facilities at NASA's Johnson Space Center. This episode features the Neutral Buoyancy Lab (NBL), which showcases how the facility is used for space station spacewalks and training, the important role of the dive teams, and how the facility will be used to prepare for the Artemis Program.