Here's why:

* Somatic cells: These are all the cells in the body except for reproductive cells (sperm and egg).

* Diploid number: Somatic cells are diploid, meaning they have two sets of chromosomes. One set comes from the mother and one from the father.

* Mitosis: Somatic cells divide through mitosis, a process that ensures each daughter cell receives a complete and identical copy of the parent cell's chromosomes.

Therefore, all cells in the organism, except for the reproductive cells (which are haploid and have half the number of chromosomes), will have 28 chromosomes.