How do I access SCI service?

As with TS clearances, Sensitive Compartmented Information (SCI) clearances are assigned only after one has been through the rigors of a Single Scope Background Investigation. SCI access, however, is assigned only in "compartments." See Compartmentalization (intelligence). These compartments are necessarily separated from each other organizationally, so an individual with access to one compartment will not necessarily have access to another. Each compartment may include its own additional clearance process.