By the very nature of secondary beams, their intensity is limited, particularly for beams of the highest interest - farthest away from stability. Active targets, which can be described as time projection chamber (TPC)-like detectors in which the detector gas is the target, have been shown to have the highest sensitivity for quantitative high-resolution studies of rare events. The physics cases that can be addressed with these devices are reviewed and some of the first results obtained with first-generation active targets are detailed. Finally some general ideas on the next generation of active targets are presented