We aim to develop a DNA hydrogel that changes structure at millimeter scale. By introducing a hairpin structure into a DNA hydrogel made by X motifs, we can expand the gel. Furthermore, by introducing a hairpin into the DNA hydrogel again, we can make it shrink. The hairpin structure can be controlled simply by adding strands. The DNA hydrogel of millimeter scale can be made and this gel can be, in theory, expand 185% in volume at the most. This realizes millimeter-scale dynamic movement of the gel, enabling it to operate on macro structures such as cells or tissues in vivo. For example, the gel can control differentiation or development by changing the distribution of cells, which is critical for them. This contributes the research of differentiation or development. In addition, the gel can also constrict blood vessel by forming and expanding inside the blood vessel. The system constricts blood vessel physically, so we can realize vasoconstrictor with fewer side effects.