University of Toronto engineers have made assembling functional heart tissue as easy as fastening your shoes. Growing heart cells in a lab is not new, but the cells are often weak and lack the shape and supports of real cells. After growing heart cells around a silk suture in a one-dimensional line, the researchers grew tissue on a 3D scaffold with T-shaped posts that poke through the honeycomb holes in a second layer, much the same as Velcro. The assembled sheets start to beat almost immediately. The ultimate goal is to create artificial tissue to repair damaged hearts.