And we join them by using our proteins in the region known as the centromere. So in this diagram, we only have four of these pairs, but for humans, we have 46 of these chromosome pairs. And each one of these individual chromosomes in the pair is also known as a chromatid, or a sister chromatid. So basically, this is one sister chromatid, and this is a second sister chromatid. This is one sister chromatid, and this is a second one, and so forth. And these cystochromatids are identical because in interface, we replicate, we use the first original to form the second replicated cystochromatid.