The article "The hydrodynamics of swimming microorganisms" by Eric Lauga and Thomas R. Powers reviews the biophysical and mechanical principles of locomotion at the small scales relevant to cell swimming (tens of microns and below). The focus is on the fundamental flow physics phenomena occurring in this inertia-less realm, emphasizing the simple physical picture. The authors review the basic properties of flows at low Reynolds number, including resistance matrices for solid bodies, flow singularities, and kinematic requirements for net translation. They also discuss classical theoretical work on cell motility, such as early calculations of swimmer speed with prescribed strokes and the application of resistive-force theory and slender-body theory to flagellar locomotion. The article outlines active research areas, including hydrodynamic interactions, biological locomotion in complex fluids, the design of small-scale artificial swimmers, and the optimization of locomotion strategies. The review aims to provide a theoretical framework for understanding the physics of locomotion at low Reynolds numbers, with a focus on analytical results and physical intuition.The article "The hydrodynamics of swimming microorganisms" by Eric Lauga and Thomas R. Powers reviews the biophysical and mechanical principles of locomotion at the small scales relevant to cell swimming (tens of microns and below). The focus is on the fundamental flow physics phenomena occurring in this inertia-less realm, emphasizing the simple physical picture. The authors review the basic properties of flows at low Reynolds number, including resistance matrices for solid bodies, flow singularities, and kinematic requirements for net translation. They also discuss classical theoretical work on cell motility, such as early calculations of swimmer speed with prescribed strokes and the application of resistive-force theory and slender-body theory to flagellar locomotion. The article outlines active research areas, including hydrodynamic interactions, biological locomotion in complex fluids, the design of small-scale artificial swimmers, and the optimization of locomotion strategies. The review aims to provide a theoretical framework for understanding the physics of locomotion at low Reynolds numbers, with a focus on analytical results and physical intuition.