The possibilities of bioengineering are endless, and one of the most energetic branches of the research community is involved in developing methods of precisely targeting therapies: "MIT engineers have outfitted cells with tiny 'backpacks' that could allow them to deliver chemotherapy agents, diagnose tumors or become building blocks for tissue engineering. ... The polymer backpacks allow researchers to use cells to ferry tiny cargoes and manipulate their movements using magnetic fields. Since each patch covers only a small portion of the cell surface, it does not interfere with the cell's normal functions or prevent it from interacting with the external environment. ... researchers worked with B and T cells, two types of immune cells that can home to various tissues in the body, including tumors, infection sites, and lymphoid tissues - a trait that could be exploited to achieve targeted drug or vaccine delivery. ... The researchers found that T cells with backpacks were able to perform their normal functions, including migrating across a surface, just as they would without anything attached. By loading the backpacks with magnetic nanoparticles, the researchers can control the cells' movement with a magnetic field."