This comprehensive review presents all modern methods for plant root research, both in the field and in the laboratory. It covers the effects of environmental interactions with root growth and function, and focuses in particular on the assessment of root distribution and dynamics. The processing of root observations, analysis and modelling of root growth and architecture, root-image analysis, computer-assisted tomography and magnetic resonance imaging, are described and discussed. Furthermore, a survey of the application of isotope techniques in root physiology is given.