Gastrulation is a fundamental morphogenetic process that establishes the three germ layers and one of the most critical events in early development. During gastrulation, cells are internalized inside of embryo through dynamic mechanisms. Xenopus has been a key model organism for studying gastrulation, providing many foundational insights into its underlying mechanisms. In this lecture, we will study how the mechanism of gastrulation has been investigated in Xenopus, and discuss how individual cells coordinate their behaviors to drive this morphogenetic movement.