FDTD modeling of ``complicated'' materials has recently gained much attention. One of the major advantages the FDTD method has over other numerical techniques is the ability to obtain wideband results using transient excitation. To obtain accurate results over a broad spectrum, it is often necessary to include the frequency dependent properties of the material (i.e., it may not be possible to treat the permittivity, conductivity, or permeability as constants over the entire spectrum). Several techniques have been proposed to account for this frequency dependence. Additionally, the use of a surface impedance boundary condition or a thin material sheet model has been shown to provide significant computational savings over a full FDTD model. Furthermore, the FDTD algorithm has been extended to account for materials that are anisotropic and nonlinear, but for those publications the interested reader is directed to the on-line database.