Mitosis is the process of cell division that produces two identical daughter cells from a single parent cell. Here's how it relates to the development of multicellular organisms:

* Growth: Mitosis allows organisms to grow by increasing the number of cells in their bodies.

* Repair: Mitosis replaces damaged or worn-out cells, ensuring the organism can heal and maintain its tissues.

* Development: From a single fertilized egg, mitosis creates all the specialized cells of an organism's body. This process of cell division and differentiation is essential for development.

In summary: Mitosis is the fundamental process that enables multicellular organisms to grow, repair, and develop from a single cell into a complex, functional being.