Duke University researchers have grown a contracting human muscle in a lab and captured it on video. The muscle acts like one found inside the body would, responding to drugs, electrical pulses and biochemical signals, according to data published Wednesday in the open-access journal eLife by Nenand Bursac and Lauran Madden. The scientists hope to use lab-grown muscles to tailor treatment plans for patients. The hope for these lab-produced muscles is that they could be used to treat patients. Doctors could grow many reproductions of a patient’s muscle, and then test drugs on each one to see which gets the best results. Other experts on the subject say this research is more of an incremental accomplishment than a huge advance, because mouse stem cells have previously been used by Bursac's team to grow muscle fibers. "I would consider it progress, certainly not a breakthrough," says Dr. Jaques Tremblay of Laval University, whose lab researches treatment for muscular dystrophies. This work builds on previous developments, because human cells behave much like mice cells do. See how they did it at Vox.