University of Wisconsin-Madison Jan 31 2026 The cells in our bodies move in groups during biological processes such as wound healing and tissue development - but because of resistance, or viscosity, those cells can't just neatly glide past each other.  Or can they? Using a pioneering method they developed to directly measure viscosity in a group of cells, University of Wisconsin–Madison engineers have made a surprising discovery that upends understanding of how cells move. It's called "negative