Horizon turns the question of the universe's scale inside out, asking what happens when physicists chase the smallest possible things rather than the largest. Scientists and researchers walk through the search for the Higgs boson, the particle proposed in the 1960s to explain why matter has mass at all, and the parallel hunt for miniature black holes that some theories predict could appear at particle colliders. The film uses these searches to test where the known laws of physics break down, moving into speculation about extra dimensions folded too small to detect directly and the possibility of parallel universes sitting alongside our own. Interviews with physicists carry the argument, laying out why something as vast as the cosmos might ultimately be explained by objects too small to see. It stays close to the open questions rather than settling them: whether these tiny, elusive objects exist at all, and what finding one would mean for how the universe is understood.