This book deals with the most widespread of root symbiosis, arbuscular mycorrhizas, an essential component of soil/plant systems occurring in the majority of plant species in natural agro-ecosystems. It is intended to aid the environmental researcher in finding relevant methods quickly, and as a general reference work it will well serve field ecologists, laboratory biologists and other workers in plant biology and soil microbiology. The volume contains the most recent advances in (I) the field of the development of biomolecular methods adapted to arbuscular mycorrhizal fungi; (II) the promotion of innovative ecological research which considers biodiversity, in order to better understand the impact of arbuscular mycorrhizas in sustainable agriculture and natural ecosystems; (III) elucidating the role of arbuscular mycorrhizas in plant development and root morphology; and (IV) defining the cellular and molecular basis of plant-fungus exchanges. An article concerning The European Bank of Glomales, an essential tool for efficient international and interdisciplinary collaboration, is also included.