Usage patterns
〈場所〉の内部を調べるto inspect the interior of a place
The police inspected the interior of the building.
内部で〈事〉が起こるfor something to happen internally (within an organization or system)
A conflict is occurring within the company.
内部に立ち入るto enter a restricted interior area
Unauthorized people are not allowed to enter the interior.
内部から〈動詞〉to do something from the inside (as opposed to externally)
It's necessary to reform the organization from within.