 Sound waves. They bring music to our ears, help doctors peer inside our bodies, and even allow us to see underwater. Now, scientists are using these versatile packets of vibrating energy for a new application, growing functional, transplantable blood vessels right on the benchtop. These engineered tissues can be used to repair injuries caused by diminished blood flow from blood clots and other blockages, but there's a lot to consider when fabricating therapeutic blood vessels. There are biological and mechanical attributes that are tricky to get right. The body's vasculature is complex and multi-scale, and a precise geometric arrangement is needed for efficient perfusion. Vessels are composed of multiple cell types, which need to be well integrated to function. To engineer tissues that meet these requirements, scientists developed a new, acoustophoretic cell patterning technique. The method uses sound waves to precisely align cells into user-defined patterns. In a new report in Nature Communications, researchers used the technique to replicate the microvessel structure found in skeletal muscle. To accomplish this, they combine human adipose-derived stem cells and endothelial cells with a biocompatible hydrogel. Before the gel solidified, the mixture was exposed to standing surface acoustic waves. These tunable sound waves directed the cells into uniform rows mimicking microvessels. As the hydrogel solidified, it held the cells in place, and they grew and matured into their new orientation. That orientation was far more anatomical than that produced by cells not exposed to the sound waves. It also enhanced microvessel-like gene expression, but the team still needed to show that artificial vasculature could help repair damage. For that, they transplanted the acoustophoretically patterned tissues into sites of ischemic injury and mice. The results were quite promising. The animal's native blood vessels actively integrated with the transplants, which provided the blood supply needed to prevent tissue loss. More work is still needed before the technique is ready for use in humans, but the study offers an important advance into the field of regenerative medicine. Using different conditions with the acoustophoretic device may also reveal ways to engineer tissues compatible with other organ systems.