Apartment (or Single-threaded apartment) Clients can call an object抯 methods only from the thread on which the object was created. Different objects from the same server can be called on different threads, but each object is called only from that one thread. Instance data is safe, global data must be protected using critical sections or some other form of serialization.The thread抯 local variables are reliable across multiple calls.Some performance benefits.Objects are easy to write, but clients can be tricky.Primarily used for controls for Web browsers.