Uniform sampling has been widely adopted in today’s circuit designs, ranging from data converters (ADC and DAC), and discrete-time signal processing (such as switched-capacitor filters). It is a well-developed processing technique that leads to many circuit architectures. However, Nyquist theory does not limit us to processing the samples at a uniform time grid so long as the average sample rate is sufficiently high, i.e., no loss of signal information. We refer data converters that sample at irregular time instants as non-uniform sampling (NUS) ADCs. In this tutorial, we will overview the basics of non-uniform sampling and the design tradeoffs for such ADC architecture. We will also examine several possible variations of NUS ADCs, and experimental results of silicon prototypes. Thanks to the unique properties of NUS, there are interesting possibilities for future circuit- and system-level architectural innovations.