Gastrulation is one of the most important phases in the life of multicellular organisms. Blastula, a single-layered cellular structure, transforms into a three-layered trilaminar structure, known as gastrula. The word "gastrula" means stomach, since the stomach (archenteron) is the first thing that forms during gastrulation. There are basically three main events that occur during gastrulation. They are as follows:1. Formation of three primary germ layers.2. A basic body plan and body axes are established. Three embryonic axes are formed namely dorsoventral, posteroanterior and left-right.3. Gastrulation movements result in a new neighborhood of cells. The formation of germ layers is the first step toward multicellular organisms. It establishes the division of tissue types. Diploblast organisms, such as coelenterates, have two germ layers (ectoderm and endoderm), while triploblastic organisms, which include all higher animals, have three germ layers (ectoderm, mesoderm, and endoderm). These germ layers are often called leaves, with the ectoderm being the outer leaf and the mesoderm being the middle leaf....