The variety of entities that is of interest to human initiatives is vast, it ranges from small to large, from hydrogen atoms and green house gases to international organizations, airplanes, production plants, software codes, etc. Some entities are solid and concrete, others are conceptual and nebulous. Some are atomic, others consist of many sub-systems, which in their turn consist of many components.
Focussing on innovation in socio-technical systems, the multi-level perspective, and (de)punctualisation in actor networks are important concepts.
Nesting is very common for (complex) interactions.
The multi-level perspective (MLP) names macro, meso and micro levels as contexts where co-evolution processes induce socio-technical transitions  .
At any MLP level, each work system  is the object of successive "clinical" interventions (in the Interaction Dictionary: regulative interactions).
For interventions that involve multiple stakeholders, the Collective Regulative Bundle Methodology is proposed. In many initiatives, development initiatives in particular, change initiatives will involve stakeholders that each act at a different level in the societal architecture (Actor Atlas). In the case of participation in ICT-reliant work systems the stakeholders' change initiatives may involve operations and ICT models as explained in the techno order ontology.
Punctualisation and Depunctialisation
In Actor-Network Theory, punctualisation refers to the effect that the components and mechanisms of certain actors are essentially hidden from view to several stakeholders interacting with it. In  the example of the automobile is used.
In a social order context, comparable punctualisations may exist for organisations and institutions.
Segment & Asset
A segment is a containing entity.
An asset is a contained entity.
For instance, money is an asset, contained in a wallet, the segment.
The notions of segment and asset are also important in the discussion on resource productivity for content.
Hierarchy & Subsidiarity