We will discuss what physics can bring to cancer biology, and the types of questions that physicists can ask such as "Why does a tumor grow where it does?" and "How does the microenvironment of a tumor affect its growth?" Cancer cells do not act alone. They get their cues from the their environment which consists of the extracellular matrix and the cells (fibroblasts) that form it. These cues can be both chemical and mechanical in nature.