Roots have been intensively studied for over one hundred years, and yet little is really known of their morphology and development in vivo. Increasing evidence suggests that there are five or more types of roots, each with distinct genetic, developmental, and physiological characteristics. The presence of these different types and the demonstration that several of the more thoroughly studied types are functionally different suggests that much of the past research on root physiology needs to be re‐examined. The evidence suggests that the roots routinely studied in laboratory experiments are normally either non‐functional in the field, or have different functional characteristics than the majority of the active roots on field grown plants.