A closure for a container, e.g., a tube, for a sample, e.g., a biological sample. The closure comprises a cap having a first opening and a second opening, the first opening capable of communicating with the mouth of a container, the second opening sealed by an exterior seal, and intermediate the first opening and the exterior seal, an interior seal. The invention also provides an assembly comprising the closure of this invention and a container. The invention also provides a method for preparing the closure.