Gradients and arrays have become very useful to the fields of tissue engineering and biomaterials. Both gradients and arrays make efficient platforms for screening cell response to biomaterials. Graded biomaterials also have functional applications and make useful substrates for fundamental studies of cell phenomena such as migration. This article will review the use of gradients and arrays in tissue engineering and biomaterials research, with a focus on cellular and biologic responses. © 2009 Bentham Science Publishers Ltd.