When living cells are placed on a surface like a culture dish, they are sensitive to what the surface is made of. As the cells spread they sense the surface by extending filapodia, small arms to probe the environment. If the surface is favorable, they will spread in that direction. In this reflection optical microscope image you can see these small arms, like tiny hairs on the edge of the cells. By changing the nature of the surface or by patterning the surface, the cells can be forced to grow or move in specific directions, which is important in developing devices to manipulate cells or even designing tissues to grow cells in. Learn more.
Photo credit: Tew Research Group, courtesy of Visual Image Library