This is an erratum to the research article "Efficient generation of single-copy human artificial chromosomes" published in Science, Volume 391, Issue 6790, March 2026. The article describes a method for the efficient generation of single-copy human artificial chromosomes (HACs) using a construct of approximately 750 kb in size. This construct is large enough to accommodate distinct types of centromere inner and outer chromatin, thereby avoiding the need for multimerization. The construct is assembled in yeast by TAR cloning in the 0.5–2 Mb range and delivered to the mammalian cell by yeast spheroplast fusion. This method achieves high efficiency of HAC formation, robust assembly of CENP-A nucleosomes, and almost complete avoidance of multimerization, in contrast to previous systems. HACs are formed without restriction to a specific cell line, such as HT1080 previously. Previous attempts suffered from multimerization and instability, which limited their use. The new approach enables precise engineering of chromosomes in mammalian cells.[1][2][4][5][6]