What is the smallest piece of reality made of?
The smallest piece of reality is a patch, a machine small enough to describe completely, with a bounded amount of state, a set of interfaces and a finite list of allowed moves. Each interface is a port, and a piece of the world has twelve. What a port shows outside is a packet, one reading from a finite set. Two ports joined make a seam, the only place a disagreement can be detected. All the readings an observer can get form its screen, and the part of its state that later moves must leave alone is its record. A patch runs one loop: read its ports, compare with its neighbors, choose a move from a printed menu, write a record, expose the result, and let anyone verify it. An outsider learns only what the boundary shows.
Also in Chapter 14: Why Twelve?.
This answer comes from OPH, Observer Patch Holography. OPH is a rigorous, consistent and complete description of the unified, self-creating computational Universe we inhabit. Its consistency is machine-checked: the fixed point at its core is constructed explicitly, and a theory with a model contains no contradiction.
To understand OPH and check every step yourself, start with the free book Reverse Engineering Reality. It builds the theory from the ground up, and the OPH Notebook answers your questions while you read.
read the free bookask the notebookor ask sage:read chapter 13: What Is One Piece of Reality Actually Made Of?watch a universe make its own particles