Biohybrid has been used as a fashionable term in scientific publications during the past years to describe a functional unit consisting of a bioactive and a structural component. The bioactive part of the biohybrid could consist of cells or bioactive molecules, while the structural part is of biological or non-biological origin. Biohybrids are currently used as implants and transplants in regenerative medicine or in vitro applications such as assays, biosensors or bioreactors. However, a clear definition of a biohybrid has not been given yet. This chapter reviews the current applications of biohybrids and identifies the challenges of biohybrids in in vivo applications. A classification of biohybrids according to their functional use and application is provided.