Big idea: data can hide patterns Large biological datasets are often too complex to understand by simply reading numbers in a table. In DREAM-High, we will eventually use heatmaps to look for patterns in breast cancer gene expression data from patients in The Cancer Genome Atlas. A heatmap can help us answer questions such as: Which samples look similar to each other? Which genes behave similarly across patients? Can visual patterns help us identify tumor subtypes? Today, we will learn this same concept using a small practice dataset that comes with R. Main idea: A heatmap turns numbers into colors, making hidden patterns and relationships easier to see.