Tissues are the basic unit of function in the body, while cells are the building blocks of tissue. Extracellular matrix is a term used to describe the extracellular matrix, which is made and secreted by groups of cells. This matrix, or scaffold, serves as a relay station for many signaling molecules in addition to supporting the cells. As a result, cells get messages from a variety of sources that emerge from the immediate environment. Each signal can set off a series of events that determine the cell's fate. Researchers have been able to manage these processes to repair damaged tissues or even create new ones by studying how individual cells respond to signals, interact with their environment, and organize into tissues and organisms. Another way to make new tissue is to utilize a scaffold that already exists. The cells from a donor organ are removed, and the collagen scaffold that remains is used to generate new tissue. This method has been used to bioengineer tissue for the heart, liver, lungs, and kidneys. This method offers a lot of promise for employing scaffolding made from human tissue lost during surgery and mixing it with a patient's own cells to create tailored organs that the immune system won't reject.