Scanning electron micrograph of the surface of garden soil. covering an area of 0.3mm x 0.2mm. Almost everything visible in the picture is a living organism. The spherical green background cells correspond to members of the Chlorophyta (green algae), such as Chlorella. Those shaped like elongated boxes with rounded tips (brown), or with straight rectangular edges (blue) are pennate diatoms. In the centre of the picture, the curving tube (pink) is the body of a nematode worm. Nematodes are simple animals found in astronomical numbers in most global ecosystems. Elsewhere, shapeless fragments (brown/green) are remnants of vegetation as yet incompletely decomposed by (invisible at this magnification) millions of bacteria. All these living components contribute to the formation of the fertile soils upon which we humans depend for our food supply.