Introduction Ribonucleic Acids (RNA) are molecules that are essential to any living organism. They are composed of nucleotides named Adenine, Cytosine, Guanine and Uracile, and usually represented as sequences over an {A, C, G, U} alphabet. In this book chapter, we provide a gentle, algorithmically self-contained, introduction into combinatorial algorithms introduced over the years to predict the secondary structure of RNA.