A microarray is a laboratory tool used to study the expression of many genes at once. It consists of a small glass or plastic slide that has thousands of tiny spots, each containing a specific DNA sequence. Researchers can apply a sample of RNA to the microarray, allowing them to see which genes are active in a particular cell or tissue type. Microarrays are valuable in various fields, including genomics, molecular biology, and medical research. They help scientists understand gene functions, identify disease markers, and develop personalized treatments. By analyzing the data from microarrays, researchers can gain insights into complex biological processes.