To understand polymers, the fundamental building blocks of our lives, both social and biological, will not only fulfill the intellectual curiosity of scientists, but more importantly help us to have a better 'life'. So it is not surprising that to understand the physical properties of polymers and polymer networks has long been a major goal of most basic and applied science and engineering disciplines. However, it has been difficult to associate polymer theories directly to experimental data. While many polymer theories only describe the motion of individual polymer chains or small polymer networks, traditional polymer experiments measure the behavior of polymers that averaged over a huge number of molecules (109--1023). This thesis focuses on the development of techniques to visualize and to manipulate single DNA molecules and biopolymer networks. These techniques allow us to directly test single polymer dynamics measurements against polymer theories and to understand the structure-mechanics relationships in polymer networks.