1. Growth and Development: Mitosis is the primary way that multicellular organisms grow. When a single fertilized egg cell divides, it creates more cells, and those cells continue to divide. This process of repeated cell division allows organisms to grow from a single cell into complex structures.

2. Repair and Regeneration: Mitosis is also essential for repairing damaged tissues. If you get a cut or scrape, your body uses mitosis to create new cells that replace the damaged ones. Mitosis can also be involved in the regeneration of lost body parts in some organisms.