Root phenomics refers to comprehensive study of plant root characteristics. Root phenomics integrated with genomics help identify molecular pathways of specific root traits and discover potential genes and genetic markers. This information can be used in plant breeding programs in developing genetically engineered crop varieties that possess desirable root traits. Traditional destructive analysis of root characteristics is very challenging as it is very capital-, labor-, and time-intensive. Two-dimensional (2D) technologies like root scanners and rhizotrons, 3D approaches like magnetic resonance imaging (MRI), X-ray computed tomography (CT), and 4D modeling help visualize and analyze root structures, in situ and nondestructively. High-throughput automated systems and robotics data pertaining to root traits help in collecting data quickly and efficiently, allowing for the analysis of large numbers of plants and root systems simultaneously, without any human error. This chapter provides an overview of various approaches used in root phenomics and their applications for improving plant growth using multi-omics technologies.