This work presents an ontological foundation of physics based on a single elementary entity: the triad. A triad is not an object, a particle, or a point in space. It is the minimal orientable process from which space, time, light, gravity, matter, and stable particles emerge. Triadic Mesh Dynamics (TMD) provides an ontology rather than a phenomenological model. It explains why physical phenomena exist, not only how they behave. This work describes the layer below the Planck scale, where triads form the fundamental structure of reality. From this layer emerge stable configurations (bulbs), corresponding to particles, and the chaotic layer of space triads, corresponding to what is currently interpreted as vacuum. The document includes:• a full derivation of the triad structure, • the growth law N(k) = 1 + 3k(k+1), • the ontological explanation of spin, time, gravity, refraction, and measurement limits, • the classification of stable and unstable bulbs (19, 37, 61A, 127A), • the interpretation of dark matter and dark energy as emergent triadic phenomena. This is the first complete description of the sub-Planckian triadic layer and its consequences for fundamental physics.