Fibers, membranes, or vessels containing living cells made by a technique called cell electrospinning are safe when used in mice, researchers find (Small 2013, DOI: 10.1002/smll.201300804). The work is a step toward use of the advanced cell-containing materials in regenerative medicine, for example, to patch damaged or aging tissues and organs. Suwan N. Jayasinghe of University College London and coworkers reported cell electrospinning earlier this year (Analyst 2013, DOI: 10.1039/c3an36599a). Previous techniques to prepare cell-containing materials seed cells onto existing structures in bioreactors. They are time-consuming and create materials with uneven cell distributions or in which some cells die. In cell electrospinning, an electrically conductive coaxial needle combines biopolymers with cells and deposits the mixture on a grounded stationary or rotating surface to form cell-containing fibers and scaffolds. The technique is faster than using bioreactors, and cells are evenly distributed in the products. The researchers now show that cells remain viable and functional in electrospun materials and that the fibers or other shapes can be transferred into mice without immune rejection or other adverse effects.