  The main physical features and operating principles of isothermal
nanomachines in microworld are reviewed, which are common for both classical
and quantum machines. Especial attention is paid to the dual and constructive
role of dissipation and thermal fluctuations, fluctuation-dissipation theorem,
heat losses and free energy transduction, thermodynamic efficiency, and
thermodynamic efficiency at maximum power. Several basic models are considered
and discussed to highlight generic physical features. Our exposition allows to
spot some common fallacies which continue to plague the literature, in
particular, erroneous beliefs that one should minimize friction and lower the
temperature to arrive at a high performance of Brownian machines, and that
thermodynamic efficiency at maximum power cannot exceed one-half. The emerging
topic of anomalous molecular motors operating sub-diffusively but highly
efficiently in viscoelastic environment of living cells is also discussed.
