This lecture explores nanotube mechanical resonators, focusing on ultrastrong coupling in the single-electron tunneling regime and backaction cooling by applying a current through the nanotube. It discusses the coupling of vibrations to single-electron tunneling, sensing mass and force, and the future potential of a mechanical qubit. The presentation delves into the quantum and classical regimes of resonators, the large coupling between vibrations and electrons, and the detection of vibrations. It also covers the energy autocorrelation, thermal vibrations, and the dramatic resonance frequency suppression. The lecture concludes with insights into electrothermal backaction, the piezoresistive heat engine and refrigerator, and the achievement of ultrastrong coupling. Various theoretical and experimental contributions are highlighted throughout the lecture.