Researchers continue to work at the blood vessel problem in tissue engineering. From the BBC: "Scientists have used human cells to grow new blood vessels in a mouse for the first time ... The ability to develop swiftly a new network of tiny blood vessels - known as capillaries - would be a prize for scientists. There are dozens of potential applications in medicine, particularly in the treatment of conditions which involve damage to a tissue's blood supply, such as that to the heart muscle following a heart attack. However, the complex structure of these vessels has slowed progress. ... What's really significant about our study is that we are using human cells that can be obtained from blood or bone marrow rather than removing and using fully developed blood vessels. ... It could certainly assist in the connection of other engineered organs to the body's blood supply. Although this approach is not yet suitable for clinical use, it is interesting that they have demonstrated you have all the elements you need to create a functional network of capillaries from a small amount of blood."