Most object-oriented systems lack two useful facilities: the ability of objects to migrate to new environments, and the ability of objects to acquire new operations dynamically. This paper proposes Knos, an object-oriented environment which supports these actions. Their operations, data structures, and communication mechanisms are discussed. Kno objects "learn" by exporting and importing new or modified operations. The use of such objects as intellectual support tools is outlined. In particular, various applications involving co-operation, negotiation, and apprenticeship among objects are described.