Living materials respond to stresses, or forces, surrounding them. If we aim to promote the growth of healthy tissue, such as in the field of tissue engineering, or limit the growth of unwanted tissue, e.g. cancerous tumors, we must understand the stresses that these tissues experience as they grow and live. How do we measure the elastic modulus of a living material? We will discuss a novel measurement technique that we developed, called cavitation rheology, which can quantitatively measure the mechanical environment of soft tissues from sub-cellular to multi-cellular length scales at arbitrary locations. We are particularly interested in applying this technique to study processes of development, disease, and damage, such as traumatic brain injuries.