This is an introductory talk aiming to review the theory of continuous deformation of C*-algebras. It concerns continuously varying C*-algebra structure on vector spaces, which includes many interesting examples such as the quantization of symplectic vector spaces, quantum groups, and twisted group algebras. We try to illuminate the basic ideas and machineries such as the theory of C([0,1])-algebras, continuous fields of C*-algebras, KK-theory, etc. utilized to derive `homotopy-invariant' information of such algebras.