Laboratories using new tissue engineering technology might be able to produce meat that is healthier for consumers and cut down on pollution produced by factory farming, researchers said. While NASA engineers have grown fish tissue in lab dishes, no one has seriously proposed a way to grow meat on commercial levels. But a new study conducted by University of Maryland doctoral student Jason Matheny and his colleagues describe two possible ways to do it. Writing in the journal Tissue Engineering, Matheny said scientists could grow cells from the muscle tissue of cattle, pigs, poultry or fish in large flat sheets on thin membranes. These sheets of cells would be grown and stretched, then removed from the membranes and stacked to increase thickness and resemble meat.