An overview is given of the quantum-dot cellular automata (QCA) architecture, along with a summary of experimental demonstrations of QCA devices. QCA is a transistorless computation paradigm that can provide a solution to such challenging issues as device and power density. The basic building blocks of the QCA architecture, such as AND, OR gates and clocked cells have been demonstrated and will be presented here. The quantum dots used in the experiments to date are metal islands that are coupled by capacitors and tunnel junctions, and devices operate only at very low temperatures. For QCA to be used in practical devices, the operating temperature must be raised, and issues such as background charge must be addressed. An introduction will be given to these issues and possible solutions.