Nanoelectromechanical systems (NEMS) are mechanical resonators at the nano-to-micrometer scale coupled to electronic devices of similar size. These systems show promise for high-speed, ultra-sensitive force microscopy and for understanding how classical dynamics emerges from quantum dynamics. This article surveys NEMS and describes their classical dynamics, focusing on weak coupling where the electronic device can be modeled as a thermal bath, despite being a driven, non-equilibrium system. NEMS include devices like the single-electron transistor (SET) coupled to a mechanical resonator, where quantum tunneling of electrons modulates the resonator's motion. These systems can detect mechanical displacements with high sensitivity, enabling applications such as magnetic resonance force microscopy (MRFM) for mapping spin densities. NEMS also have potential in mass sensing, with recent achievements in attogram-level detection. NEMS are interesting as non-trivial dynamical systems, with quantum effects emerging at cryogenic temperatures. The mechanical resonator's center-of-mass can be driven into quantum states, such as superpositions of position states, when interacting with quantum-coherent electronic devices. The quantum nature of these systems is reflected in the measured current, with nanomechanical resonators containing up to ten billion atoms, making quantum effects macroscopic in scale. In the weak coupling regime, the electronic device behaves as a thermal bath, leading to thermal Brownian motion of the resonator. This allows the use of equilibrium concepts to model non-equilibrium systems, providing insights into classical dynamics emerging from quantum dynamics. The article discusses various NEMS, including tunneling electrodes, quantum point contacts, and charge shuttles, highlighting their coupled dynamics and the role of mechanical and electronic degrees of freedom. The SET-mechanical resonator system is analyzed, with the master equation describing the probability distribution of the resonator's state. In the steady state, the SET behaves as a thermal bath, leading to Gaussian-like probability distributions for the resonator's position and velocity. The effective temperature of the SET is determined by the measured current, and the system's dynamics are influenced by the separation of timescales between the oscillator and SET. In the weak coupling regime, the SET acts as a thermal bath, damping the oscillator's motion. The analysis shows that the SET's influence on the oscillator can be modeled using classical equations, with the oscillator's dynamics governed by the effective temperature and the separation of timescales. This understanding is crucial for developing NEMS for applications in metrology, force microscopy, and quantum dynamics studies.Nanoelectromechanical systems (NEMS) are mechanical resonators at the nano-to-micrometer scale coupled to electronic devices of similar size. These systems show promise for high-speed, ultra-sensitive force microscopy and for understanding how classical dynamics emerges from quantum dynamics. This article surveys NEMS and describes their classical dynamics, focusing on weak coupling where the electronic device can be modeled as a thermal bath, despite being a driven, non-equilibrium system. NEMS include devices like the single-electron transistor (SET) coupled to a mechanical resonator, where quantum tunneling of electrons modulates the resonator's motion. These systems can detect mechanical displacements with high sensitivity, enabling applications such as magnetic resonance force microscopy (MRFM) for mapping spin densities. NEMS also have potential in mass sensing, with recent achievements in attogram-level detection. NEMS are interesting as non-trivial dynamical systems, with quantum effects emerging at cryogenic temperatures. The mechanical resonator's center-of-mass can be driven into quantum states, such as superpositions of position states, when interacting with quantum-coherent electronic devices. The quantum nature of these systems is reflected in the measured current, with nanomechanical resonators containing up to ten billion atoms, making quantum effects macroscopic in scale. In the weak coupling regime, the electronic device behaves as a thermal bath, leading to thermal Brownian motion of the resonator. This allows the use of equilibrium concepts to model non-equilibrium systems, providing insights into classical dynamics emerging from quantum dynamics. The article discusses various NEMS, including tunneling electrodes, quantum point contacts, and charge shuttles, highlighting their coupled dynamics and the role of mechanical and electronic degrees of freedom. The SET-mechanical resonator system is analyzed, with the master equation describing the probability distribution of the resonator's state. In the steady state, the SET behaves as a thermal bath, leading to Gaussian-like probability distributions for the resonator's position and velocity. The effective temperature of the SET is determined by the measured current, and the system's dynamics are influenced by the separation of timescales between the oscillator and SET. In the weak coupling regime, the SET acts as a thermal bath, damping the oscillator's motion. The analysis shows that the SET's influence on the oscillator can be modeled using classical equations, with the oscillator's dynamics governed by the effective temperature and the separation of timescales. This understanding is crucial for developing NEMS for applications in metrology, force microscopy, and quantum dynamics studies.