Biocompatibility refers to whether a material is compatible with biological tissue. Biocompatible materials do not produce a toxic or severe immune responses when exposed to the body or bodily fluids. This is extremely important for implantable devices as entire biological systems can become non-functional due to toxicity or an adverse reaction to a foreign material. In some cases, the bodie's foreign body response can also render important implanted devices useless. Some important components of biocompatibility include evaluation of cytotoxicity (does the material cause cell death?), genotoxicity (does the material cause alteration of the genome DNA?), carcinogenicity (does the material cause cancer?), and immunogenicity (does it provoke an immune response?).