Brownian circuits are circuits that use noise and fluctuations as an active mechanism in their operation. While in traditional circuits noise is kept under control by suppressing it, such a modus operandus has become less suitable with the progress in integration densities of electronics. In circuits with nanometer-scale feature sizes it is expected that noise has such high levels that alternative methods will become necessary. This paper gives a short review of research efforts in this framework, with a focus on work by ourselves.