Cell migration is an extremely complex phenomenon. A motile single cell, or multicell aggregate, that penetrates through the extracellular matrix of neighboring tissues can be described as invasive. Cells grouped into coherent sheets, strands, or tubes may undergo a form of collective cell migration governed by tight intercellular connections. The former mechanism is characteristic of metastatic growth, while the latter is associated with wound healing. How can seemingly similar cellular mechanisms result in such dramatically different outcomes?