Genomics, a baby born about 4.5 min ago in the 24-h timeline of crop improvement, is a collection of tools for inspection and dissection of genome structure and function. The technology boom in DNA sequencing has provided plant breeders with vast data on the structure, function and variation of genomic content in breeding populations, which are efficiently utilized in many major crop species for high-resolution genetic map construction, alignment of genetic and physical map, genomic variant identification, association analysis, mutant population generation and selection of superior genotypes using genome information. This chapter provides an overview of major areas of genomics and current applications of genomics tools in germplasm characterization, genetic mapping and quantitative trait loci (QTL) identification, mutant population development, genome-wide association analysis and genomic selection. We carefully avoided genome editing and transgenic technologies as these are separate technological branches that use gene sequence information as input but use an engineering approach to alter genetic makeup. Finally, current and possible future applications of genomics tools in evaluating crop wild relatives are discussed.