Why nematodes? Soil provides many ecological services essential for agriculture. Some services, such as soil mixing and the recycling of nutrients, are supplanted by farming practices. Other services, such as biodegrading pesticides and impeding nitrate leaching, are difficult to mimic so farmers rely on natural soil processes. The quality and ‘health’ of a soil can be evaluated by measuring variables reflecting the service, e.g. plant-available N, rates of decomposition, nitrate levels in groundwater, or by taking stock of the soil organisms that collaborate to provide the service. Microbes, particularly bacteria, are the life forms most responsible for mineralization, decomposition, regulation of noxious organisms, and immobilization of nutrients destined for groundwater, but they are difficult to capture and even more challenging to quantify. Larger life forms, such as beetles and earthworms, are relatively easy to study and their population dynamics may track that of microbes, but only loosely since they do not rely on microbes for their diet. The search for easy-to-study organisms with activities and abundance reflective of microbial communities led ecologists to nematodes, a most diverse and successful phylum only one step above microbes in the soil food chain and represented in every soil on earth.