Scientists have been hankering after that in vitro burger for at least five years, and what they have is a tardy order for a patty expected to cost over $300,000. Now, biotech company Modern Meadows is focusing on another lab-grown cow product: leather. Tanned hide should be technologically simpler to manufacture in the lab than medium-rare muscle, the company hopes, as well as more appealing to consumers.To make leather in vitro, the company plants to start with a biopsy from a cow, grow the bovine cells in the lab and shape them into sheets of fused cells, perhaps with the aid of a 3D bioprinter, a machine that builds cells into tissues. Next, in a bioreactor, they will stimulate the tissue to differentiate into skin and muscle. Finally, they will cut away the meat and tan the hide. The company hopes to have an in vitro leather production facility going within the next five years---though they didn't say how much leather they were planning to make, or what it might cost. Lab-grown bomber jackets, coming soon?