A three-envelope package for preserving tissue specimens or other sterile objects. A sterile tissue sample is sealed within an innermost envelope sterile inside and out. The innermost envelope is sealed within the sterile interior of an intermediate envelope equipped with a peel-back seal for subsequent opening. Both the inside and the outside of the intermediate envelope are sterile. The intermediate envelope is sealed within the sterile interior of an outermost envelope, made of foil or another substance impermeable to a storage medium, such as liquid nitrogen. The outermost envelope provides complete impermeability to liquid nitrogen, eliminating the possibility of nitrogen seepage through the peel-back seal of the intermediate envelope. When the envelope package is removed from storage, the intermediate envelope is removed from the outermost envelope and can be opened in an assumed non-sterile environment, without contaminating the innermost envelope or the tissue specimen therein.