Cell manipulation is one of the major concerns in medicine, pharmaceuticals, and tissue engineering. Since the extracellular matrix (ECM) plays a pivotal role in regulating cell behavior and function, as well as various soluble bioactive substrates, in vitro reconstitution of ECM with intrinsic functions has been in great demand for medical, pharmaceutical, and tissue engineering applications. However, reconstitution is not easy by conventional chemical and physical methods due to the compositional and structural complexity of the ECM. For this reason, the decellularization technique is increasingly focused upon. In this chapter, we summarize the structures, compositions and functions of the ECM. Additionally, trials mimicking the ECM will be briefly addressed.