Where the UUCG tetraloop is a loner, the GNRA tetraloop is gregarious. Where UUCG accommodate few substitutions, GNRA can accept many. GNRA often makes long-range hydrogen-bonding interactions to other RNA elements, the most famous being the tetraloop receptor. The GNRA tetraloop illustrates how RNA:RNA interactions work, while the UUCG tetraloop illustrates how RNA can be self-contained. These tiny RNAs have mighty roles in the biology of RNA!