A biosimilar is a biological medical product that is almost an identical copy of an original product that is manufactured by a different company. Biosimilars are officially approved versions of original "innovator" products and can be manufactured when the original products patent expires. Biosimilars are similar to generic drugs, but there are important differences. Unlike generic drugs, biosimilars are not exact copies of their brand name drug. Biologics are highly complex molecules that are grown rather than synthesized and have an inherent level of micro-variability. Because of this variability in the structure of reference biologics, biosimilars cannot be exact copies. Instead, biosimilars mimic the active ingredient in the reference biologic. Biosimilars are highly similar to the reference product in terms of structure, biological activity, efficacy, safety, and immunogenicity profile. The FDA and the EMA have specific standards for biosimilars that must be met. Biosimilars are safe and effective treatment options for many illnesses such as chronic skin and bowel diseases, arthritis, kidney conditions, and cancer.