In vitro selection and structure-based searches have emerged as useful techniques for the discoveries of structurally complex RNAs with high affinity and specificity toward metabolites. Here, we focus on the design of a human genomic library that serves as the DNA template for in vitro selection of RNA aptamers. In addition, the structural solutions obtained from the in vitro selection can be used for structure-based searches for discovery of analogous aptamers in various genomic databases.