A nucleosome is a fundamental unit of DNA packaging in eukaryotic cells. It consists of a segment of DNA wrapped around a core of histone proteins, forming a structure that resembles "beads on a string." This arrangement helps to compact the DNA, allowing it to fit within the cell nucleus while also playing a role in gene regulation. Nucleosomes are essential for the organization of chromatin, which is the complex of DNA and proteins that make up chromosomes. By controlling the accessibility of DNA, nucleosomes influence processes such as gene expression and DNA replication, ensuring that the genetic information is properly managed within the cell.