Putting the genome on the map

The maps of our everyday lives are much more than just linear lists of place names. Instead, their colours, symbols, contours and grid lines seek to describe different types of landscape, and to depict the spatial relationships between structural and functional landmarks of the environment (Fig. 1). It was the combination of photography and aviation that revolutionized mapmaking in the early part of this century. In much the same way, it is fluorescence microscopy and digital imaging (Box 1) in combination with molecular genetics that is driving our emerging view of the genome in space and time