This chapter delves into the intriguing world of RNA, emphasizing its discovery, structural components, and multifaceted functions. The narrative begins with the historical milestones marking RNA’s discovery in the late nineteenth century, tracing its evolution from being overshadowed by DNA to recognition as a central molecule in genetic regulation and expression. This chapter proceeds to explain the building blocks of RNA—nucleotides, which consist of a ribose sugar, a phosphate group, and one of four nitrogenous bases: adenine, guanine, cytosine, or uracil. These components are outlined in detail, highlighting how their specific arrangements define the structure and function of various RNA types. Focusing on RNA function, this chapter provides an overview of the diverse roles RNA plays in cellular machinery and genetic regulation. It discusses RNA’s role in protein synthesis through messenger RNA (mRNA), its structural contributions via ribosomal RNA (rRNA), and its involvement in amino acid transport through transfer RNA (tRNA). Additionally, this chapter explores the regulatory functions of non-coding RNAs, such as microRNAs and long non-coding RNAs, which play critical roles in gene expression and epigenetic regulation. By integrating historical context with detailed descriptions of RNA’s molecular structure and function, this chapter aims to provide readers with a comprehensive understanding of RNA’s essential role in biology. It sets the stage for further exploration of RNA’s potential in advancing genetic research and medical therapies, highlighting its importance in the past, present, and future of biological sciences.