Transfer RNA (tRNA) is a key molecule to decode the genetic information on mRNA to amino acids (protein) in a ribosome.  For tRNA to fulfill its adaptor function, tRNA should be processed into the standard length, post-transcriptionally modified, and aminoacylated (tRNA maturation steps) by the relevant enzymes with excellent substrate specificity.  Especially, the modification step is essential for the tRNA to maintain the canonical L-shaped structure, to ensure the correct codon-anticodon pairing, and to be specifically recognized by the cognate aaRS, which is required for the decoding function of tRNA.  Recent genome analyses and post-genome (proteomics and ribonucleomics) analyses have identified genes involved in the tRNA processing, modification, and aminoacylation.  Furthermore, post-genomic structural analysis has elucidated the structural basis for the tRNA maturation mechanism.  Here we present our recent progress of the structural biology of the tRNA maturation.