Non-coding RNAs (ncRNAs) are RNA molecules that are not translated into proteins. They are divided into two categories, namely, housekeeping ncRNAs and regulatory ncRNAs. The main function of the ncRNAs is to maintain the normal cell functionalities. Small RNAs, ribosomal RNAs (rRNAs), long ncRNAs and transfer RNAs are some types of non-coding RNAs, which are abundant and functionally significant. Numerous types of small and long non-coding RNAs are considered important regulators of gene expression in a variety of processes, which range from embryonic development to innate immunity. This promotion of gene expression is done by a special ncRNA named enhancer RNA, which is transcribed from the enhancer region of the gene. The human genome is encoded with thousands of small and long RNA transcripts that do not code for proteins. This book explores all the important aspects of regulatory non-coding RNAs. It will prove to be immensely beneficial to students and researchers studying this topic.