The key topics of this article are object composition and mobility. Its main concern is a concept-based presentation of a simple component architecture that has evolved from project Oberon, an integrated language and system project in the heritage of Pascal and Modula. Some of the highlights specially focussed on are a notion of fully hierarchic compound objects, persistent object representation, object construction methods, mobile objects and, in particular, a new and very effective approach to portable code in combination with dynamic compilation. A novel combination of generic object interfaces and hierarchic message processing in compound objects provides a uniform solution to a diversity of archetypal problems.