Reproductive cells, also known as gametes, have 23 chromosomes. This structure is called haploid.

Here's why:

* Haploid means having only one set of chromosomes.

* Diploid means having two sets of chromosomes.

* Human body cells (somatic cells) are diploid, with 46 chromosomes (23 pairs).

* Gametes (sperm and egg cells) are haploid, with 23 chromosomes.

When a sperm cell (haploid) fertilizes an egg cell (haploid), the resulting zygote is diploid, with 46 chromosomes.