Currently, we have two main interests: the identification and characterization of small noncoding RNAs and the identification and characterization of small proteins of less than 50 amino acids. For two reasons, small RNAs and small proteins have been overlooked. First, biochemical assays do not detect these small molecules. Second, genome annotation misses the corresponding genes, which are poor targets for genetic approaches. However, mounting evidence suggests that both classes of these small molecules play important regulatory roles.