Regeneration is the process of renewal, restoration, and growth that makes genomes, cells, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. Regeneration can either be complete or incomplete. In complete regeneration the new tissue is equivalent to the lost tissue. In incomplete regeneration after the necrotic tissue comes fibrosis. Tissue regeneration is the process of renewal and growth to repair or replace tissue that is damaged or suffers from a disease.