Migrasomes are newly discovered organelles of migrating cells. When a cell migrates, numerous long membrane tethers named retraction fibers are pulled out from the trailing edge of the cell. Large vesicles named migrasomes grow on the retraction fibers. Migrasomes are connected to the retraction fibers and contain numerous intraluminal vesicles, which give migrasomes their characteristic morphological feature.

During embryonic development, the precise regulation of various complex pattern depends on the expression, secretion and spatiotemporal regulation of a large number of signal molecules, especially the vascular system. The expanded vascular network must sprout and branch frequently to ensure that all tissues can obtain adequate blood supply. Most important, this expanded vascular network must comply with strict structural patterns to match specific tissue structures. The heart and lung are good examples, where the matching relationship between blood flow branches and the distribution of myocardial cell and alveoli is critical for their function, but little is known about how this matching pattern is formed. The vascular system is the first functional organ developed in the embryo and is critical for nutrients and oxygen supply. Vascular branching morphogenesis relies on the precise localization of secreted modulators of epithelial growth to select branch sites and direct branch elongation, but the intercellular signals that control blood vessel branching have not been previously identified. The establishment of the concentration gradient of angiogenic factor is the key to design the branch point and form the new vascular network to match the corresponding tissue structure.