Bacteria perform chemotaxis utilizing core two-component signaling systems to which have been added enhanced features of signal amplification, sensory adaptation, molecular memory and high sensitivity over a wide dynamic range. Chemoreceptors are central to the enhancements. These transmembrane homodimers associate in trimers and in clusters of signaling complexes containing from a few to thousands of receptors. Bacterial chemotaxis is mediated by two-component systems for which the capabilities of histidine kinase-response regulator signaling have been enhanced by additional components and protein modifications. With these, chemotaxis sensory systems exhibit signal amplification and sensory adaptation, detect temporal gradients through a molecular memory and respond with high sensitivity over a wide dynamic range. Chemoreceptors are central to these expanded capabilities. They carry sites of covalent modification that enable molecular memory, sensory adaptation and wide dynamic range. Receptors are homodimers that form trimers and higher order clusters of signaling complexes, structures in which interactions create signal amplification, cooperative sensing and cross-receptor adaptational assistance. This review summarizes recent progress in understanding chemoreceptors.