As I might have remarked once or twice, the efficient construction of blood vessels is a crucial infrastructural goal for the field of tissue engineering. Further progress absolutely depends upon it: "The work focuses on vascular tissue, which includes capillaries, the tiniest blood vessels, and is an important part of the circulatory system. The team has created a surface that can serve as a template to grow capillary tubes aligned in a specific direction. ... The surface is patterned with ridges and grooves that guide the cells' growth. ... The cells, known as endothelial progenitor cells (EPCs), not only elongate in the direction of the grooves, but also align themselves along the grooves. That results in a multicellular structure with defined edges, also called a band structure. Once the band structures form, the researchers apply a commonly used gel that induces cells to form three-dimensional tubes. Unlike cells grown on a flat surface, which form a network of capillary tubes extending in random directions, cells grown on the nano-patterned surface form capillaries aligned in the direction chosen by the researchers."