Here's why:

* Humans have 46 chromosomes in total, arranged in 23 pairs.

* Egg cells (and sperm cells) are called gametes. They are produced through a process called meiosis, which halves the number of chromosomes.

* Therefore, each gamete has 23 chromosomes, one from each of the original 23 pairs.

This ensures that when an egg is fertilized by a sperm cell (also containing 23 chromosomes), the resulting zygote will have the correct number of chromosomes (46).