various steps in our analysis within a concrete model theory.

The paper is organized as follows. In the next section we analyse the basic substratum, i.e. the microscopic patterns of vacuum fluctuations, in particular the [negative]{} energy fluctuations. In section \[worm\] we describe the three different roads which lead (in our view: inevitably) to the concept of [wormhole space]{}. The preparatory sections 2 and 3 are then amalgamated in section 4 into a detailed analysis of the microscopic distribution pattern of [short-cuts]{} or [wormholes]{} and their consequences for the number of [effective]{} DoF in a volume of space. We introduce a new type of dimension, the so-called [holographic dimension]{}. Furthermore, we explain the microscopic basis of the [holographic principle]{} in general and the [bulk-boundary correspondence]{} between the DoF in the interior of e.g. a BH and the DoF on the boundary. Some apparent counter examples concerning the area-scaling property (see e.g. [@Marolf]; Wheeler’s ’bag of gold’-spacetimes ) are very briefly addressed. In the last section we briefly comment on a number of immediate applications of our microscopic holographic approach and (open) problems which can be settled with the help of our framework.

The Structure of the Vacuum Fluctuations on a 