Metamorphosis has allowed insects to become the biggest group of land organisms on the planet in terms of species number,overall numbers as well as to have a global distribution and huge diversity of living habits.Metamorphosis allows insects to have completely different morphological features,structures,functions and living habits at different life-stages,which greatly expands their behavioral and ecological range.Metamorphosis is a result of long-term adaption to the natural environment and co-evolution.Metamorphosis is accurately regulated by insect hormones,nutrients and gene expression.This review provides a brief introduction to the types of metamorphosis,its regulation by hormones,nutrients and genes,and the scientific and practical significance of research on metamorphosis.