This article proposes the concept of 'event' as the ontological mechanism of the emergence of the new in dialectical materialism. The central problem is the development paradox formulated by V. V. Orlov: if new content is present at a lower stage of material development, how does it arise at a higher stage if it is not present in the lower stage, either actually or as a hidden potency? Neither Soviet diamat – a 'plenary' materialism that excludes structural void – nor Western Marxism provides a satisfactory mechanism: the former postulates development teleologically, the latter merely registers contingency. The novelty of the approach lies in treating the event as immanent to the ontology of matter – as the singular actualization of a structural possibility defined by the split of being and non-being. The article combines analysis of historical-philosophical sources (Democritus's and Epicurus's atomism, the concept of δέν, clinamen, Plato's dodecahedron) with concrete scientific material (Norton's Dome, Penrose aperiodic tilings, the spacetime quasicrystal hypothesis). The main result is that aperiodicity – the absence of translational symmetry – is established as a universal property of matter enabling qualitative development. Democritus's δέν is read as the ontological correlate of this property. The conclusion is that introducing the event concept into the categorical apparatus of dialectical materialism fills a gap left open by the treatment of development as an attribute of the matter.