Book excerpt: This new edition of Fungal Associations focuses on mycorrhizas, lichens and fungal-bacterial symbioses. It has been completely revised, updated and expanded. Renowned experts present thorough reviews and discuss the most recent findings on molecular interactions between fungi and plants or bacteria that lead to morphological alterations and novel properties in the symbionts. New insights into the beneficial impact of fungal associations on ecosystem health are provided and documented with striking examples.