The law of accession and accessories in a wider sense determines the legal fate of property forming an integral or a functional unity. Integral unification may change the attribution of ownership. By contrast, functional unity merely links the legal fate of two separate objects of property law, thus creating a certain "parallelism". The present study examines the constitutive elements of these two types of connections, their proprietary effects and the constructive principles through which French and German law unify or coordinate the legal fate of (formerly) separate objects of property. Furthermore, it discusses the differing perspectives regarding the central issues of the law of accession and accessories and the resulting fundamental concepts and guiding principles underlying this law in the different legal orders studied.