We are in the midst of a second quantum revolution, building on the first, which established the rules of quantum mechanics. The second revolution will use these principles to develop new technologies. This review discusses the principles and tools of quantum technology, including quantum information technology, quantum electromechanical systems, coherent quantum electronics, quantum optics, and coherent matter technology. Quantum technology allows us to control complex systems governed by quantum physics, unlike classical technology. Two key drivers are miniaturization and the potential for vastly improved performance over classical systems. The second quantum revolution marks a shift from passive observation to active manipulation of quantum states. Quantum mechanics enables new technologies such as quantum computing, cryptography, and sensors. Quantum information technology, rooted in quantum entanglement, has led to breakthroughs in quantum computing and cryptography. Quantum algorithms like Shor's and Grover's offer exponential and quadratic speedups, respectively. Quantum cryptography provides secure communication through the Heisenberg Uncertainty Principle. Quantum information theory explores the limits of information processing in quantum systems. Quantum electromechanical systems (QEMS) enable high-sensitivity measurements, while coherent quantum electronics explores quantum transport and devices. Superconducting circuits and quantum dots are promising for quantum computing. Quantum optics and photonics enable new imaging and communication technologies. Coherent matter technology, including atom optics and gravity gradiometry, has applications in sensing and navigation. The field is still in its early stages, with much research needed to develop practical quantum technologies. The second quantum revolution promises transformative advances in computing, communication, and sensing.We are in the midst of a second quantum revolution, building on the first, which established the rules of quantum mechanics. The second revolution will use these principles to develop new technologies. This review discusses the principles and tools of quantum technology, including quantum information technology, quantum electromechanical systems, coherent quantum electronics, quantum optics, and coherent matter technology. Quantum technology allows us to control complex systems governed by quantum physics, unlike classical technology. Two key drivers are miniaturization and the potential for vastly improved performance over classical systems. The second quantum revolution marks a shift from passive observation to active manipulation of quantum states. Quantum mechanics enables new technologies such as quantum computing, cryptography, and sensors. Quantum information technology, rooted in quantum entanglement, has led to breakthroughs in quantum computing and cryptography. Quantum algorithms like Shor's and Grover's offer exponential and quadratic speedups, respectively. Quantum cryptography provides secure communication through the Heisenberg Uncertainty Principle. Quantum information theory explores the limits of information processing in quantum systems. Quantum electromechanical systems (QEMS) enable high-sensitivity measurements, while coherent quantum electronics explores quantum transport and devices. Superconducting circuits and quantum dots are promising for quantum computing. Quantum optics and photonics enable new imaging and communication technologies. Coherent matter technology, including atom optics and gravity gradiometry, has applications in sensing and navigation. The field is still in its early stages, with much research needed to develop practical quantum technologies. The second quantum revolution promises transformative advances in computing, communication, and sensing.