Asymmetric localization of mRNA is a mechanism to regulate gene expression spatially as well as temporally. To study localization mechanisms various probes for RNA imaging have been established. Protein-based probes fused to split fluorescent reporters are suitable, since they can be expressed by the cellular machinery. Sequence-specific binding of proteins to their target RNA and subsequent reconstitution of the fluorescent reporter allow RNA detection. However, the traditional fluorescent reporters based on split-GFP are large and self-assemble spontaneously, causing significant background. To circumvent these limitations we used the three-body split-GFP by Geoffry Waldo at Los Alamos Labs and developed the Tetramolecular Fluorescence Complementation (TetFC) reporter system for detection of specific RNAs in vitro. In this video we show the concept of this system and how it is performed in the laboratory. The detection of a specific RNA is monitored via fluorescence intensity measurements and in-gel fluorescence. We thank the “Sea Life Deutschland GmbH” for the opportunity to film at the SEA LIFE Timmendorfer Strand. The jellyfish shown in this video is Aurelia aurita (and not Aequorea victoria from which GFP was first isolated).