Abstract: Single molecule manipulation tools such as optical tweezers, magnetic tweezers, micropipettes and Stokes dragging are reviewed. These tools have been used to stretch, rotate and unzip DNA in order to understand the mechanical properties of single DNA molecules. They have also been used to study the mechanisms of molecular motors such as DNA polymerases, RNA polymerases, topoisomerases, and chromatin remodeling complexes. These protein machines are of great importance for some basic life processes.