A team of MIT researchers has found a way of precisely controlling lab grown microfibers making it possible to grow complex structures that are optimally designed for particular applications. The researchers were able to control and vary both the size and composition of individual wires as they grew. Nanowires are grown by using "seed" particles, metal nanoparticles that determine the size and composition of the nanowire; by adjusting the amount of gases used in growing the nanowires, scientists were able to control the size and composition of the seed particles and, therefore, the nanowires as they grew. Using a process called electron tomography, they were able to reconstruct the three-dimensional shape of individual nanoscale wires. The scientists comment that their findings can be used in more energy efficient low-cost LED lights and low-cost solar energy panels.