Feeder cells. Coloured scanning electron micrograph (SEM) of feeder cells (red). Feeder cells are fibroblasts that are used to help culture embryonic stem cells. Embryonic stem cells are capable of becoming any cell in the body. Feeder cells, which are treated so that they are unable to divide, provide biochemical signals that prevent the stem cells from differentiating while keeping them dividing until there are a sufficient number present for research. Human embryonic stem cells are a potential source of cells to repair damaged tissue in diseases such as Parkinson's and insulin-dependent diabetes. Magnification: x525 when printed 10 centimetres wide.