Research and Development
From Kerbal Space Program Wiki
The Research and Development Facility is a new structure added in version 0.22. The building is used to unlock new parts in the tech tree in career mode. Unlocking parts requires science. The facility contains multiple buildings, but it is not possible to go inside each individual building. The R&D facility is the largest building in the KSC.
Secondary Buildings
The Research and Development Facility is the second structure to contain multiple buildings, after the tracking station.
Trivia
If a player tries to enter the R&D facility in sandbox mode, a message will appear saying "The research and development facility is closed".