Stromal cells, or mesenchymal stromal cells, are differentiating cells found in abundance within bone marrow but can also be seen all around the body. Stromal cells can become connective tissue cells of any organ, for example in the uterine mucosa (endometrium), prostate, bone marrow, lymph node and the ovary. They are cells that support the function of the parenchymal cells of that organ. The most common stromal cells include fibroblasts and pericytes. The term stromal comes from Latin , "bed covering", and Ancient Greek , , "bed". Stromal cells are an important part of the body's immune response and modulate inflammation through multiple pathways. They also aid in differentiation of hematopoietic cells and forming necessary blood elements. The interaction between stromal cells and tumor cells is known to play a major role in cancer growth and progression. In addition, by regulating local cytokine networks (e.g. M-CSF, LIF), bone marrow stromal cells have been described to be involved in human hematopoiesis and inflammatory processes. Stromal cells (in the dermis layer) adjacent to the epidermis (the top layer of the skin) release growth factors that promote cell division. This keeps the epidermis regenerating from the bottom while the top layer of cells on the epidermis are constantly being "sloughed" off the body. Additionally, stromal cells play a role in inflammation responses, and controlling the amount of cells accumulating at an inflamed region of tissue. Defining a stromal cell Defining a stromal cell is of importance because it was a source of difficulty in the past. Without a strong definition studies could not cross over or gain knowledge from each other because a stromal cell was not well defined and went by a plethora of names. A stromal cell is currently more specifically referred to as a mesenchymal stromal cell (MSC). It is non-hematopoietic, multipotent, and self-replicating. These factors make it an effective tool in potential cell therapies and tissue repair. Being a mesenchymal cell indicates an ability to develop into various other cell types and tissues such as connective tissue, blood vessels, and lymphatic tissue. Some stromal cells can be considered stem cells but not all therefore it can not be broadly termed a stem cell. All MSCs have the ability adhere to plastic and replicate by themselves. The minimal criteria to define MSCs further include a specific set of cell surface markers. The cells must express CD73, CD90 and CD105 and