 Exact solutions to Maxwell's equations are known only for special geometries such as spheres, spheroids, or cylinders, so approximate methods are in general required.However, the DDA employs no physical approximations and can produce accurate enough results, given sufficient computer power.The basic idea of the DDA was introduced in 1964 by DeVoe

who applied it to study the optical properties of molecular aggregates; retardation effects were not included, so DeVoe's treatment was limited to aggregates that were small compared with the wavelength.