When a fertilized egg is developing into a fetus, cell populations forming tissues are in a fluid state, and thus, the tissue can be easily deformed. Cells also generate mechanical forces during development that contribute to the shaping of the tissues and organs. An important question is how organisms secure/proceed with proper tissue and organ formation in these conditions. In order to understand the process of tissue and organ formations, it is essential to understand how physical characteristics of tissues responding to mechanical stresses influence the process of organogenesis.