This chapter provides the time-delay approach to sampled-data and network-based control. The chapter starts with preliminaries on three main approaches to sampled-data control. The delay corresponding to sampled-data control can be considered as a piecewise-continuous fast-varying delay. A novel (comparatively to fast-varying delays) Lyapunov-based analysis that takes into account the sawtooth dynamics of this delay is presented in Sects. 7.2–7.4. In Sects. 7.5–7.7 the time-delay approach is extended to NCSs, where variable sampling intervals and network-induced delays, as well as protocol scheduling and quantization are taken into account.