This document discusses in vitro transcription and fluorescent in situ hybridization (FISH) techniques for visualizing gene expression in tissue samples. It describes the process of designing gene-specific primers, amplifying the gene of interest via PCR, synthesizing fluorescently-labeled RNA probes from the PCR product, hybridizing the probes to tissue samples, and using fluorescence microscopy to visualize where in the tissue the gene is expressed at a cellular level. The document provides technical details on each step of the process and discusses ways to optimize and troubleshoot the technique.