Live-cell fluorescence microscopy capturing a mitochondrial fusion event during Saccharomyces cerevisiae mating. The left cell expresses a nuclear-encoded, soluble matrix marker (mKate2), while the right cell expresses a mitochondrial genome (mtDNA)-encoded fusion protein, Atp6-mNeonGreen. Following mitochondrial fusion, the red matrix protein rapidly equilibrates throughout the newly unified network. In stark contrast, the mtDNA-encoded Atp6-mNeonGreen exhibits highly restricted diffusion, remaining localized to its original mitochondrial territory. This observation provides visual evidence for the 'Sphere of Influence' hypothesis, suggesting that mtDNA-encoded proteins remain spatially coupled to their cognate genomes.