Soil is a fundamental and critical component of terrestrial ecosystems, but one that is often overlooked. It is an extremely complex environment, both in terms of its physical structure and in that it supports levels of biodiversity far greater than those found above ground in any ecosystem. Bringing together existing knowledge across many areas of soil biology and physics, this book develops the concept of soil architecture and explores key characteristics of the remarkable `inner space' of the soil. The authors consider how such structure develops through time and the consequences this has for life underground. They also explore the interactions between the biological and physical components of the soil and how they relate to its many functions, in order to demonstrate the key role of soil architecture in underpinning ecosystem dynamics. The diverse but richly interrelated perspectives offered in this book make it an essential resource for researchers and students in soil and environmental sciences, terrestrial ecology, plant sciences and microbiology.