An important challenge in many applications, ranging from biomedical devices to ship hulls, is the prevention of nonspecific biomolecular and microorganism attachment on surfaces. For example, nonspecific protein adsorption degrades the performance of surface-based diagnostic devices and causes an adverse effect on the healing process around implanted biomaterials. To address this challenge, our goals are twofold. First, we strive to provide a fundamental understanding of nonfouling mechanisms at the molecular level using an integrated experimental and simulation approach. Second, we aim to develop biocompatible and environmentally benign ultra low fouling materials based on the molecular principles we have learned. Over the last few years, we have demonstrated that zwitterionic and mixed charge materials and surfaces are highly resistant to nonspecific protein adsorption, cell adhesion and bacteria adhesion/biofilm formation from complex media. Both simulation and experimental results show that the strong hydration of zwitterionic materials is responsible for their excellent nonfouling properties. In addition to their excellent nonfouling properties, zwitterionic carboxybetaine-based materials have functional groups for direct ligand immobilization while the cationic precursors of zwitterionic materials have self-sterilizing capabilities. Superhydrophilic zwitterionic materials are also shown to have unique advantages for stealth nanoparticles over their amphiphilic poly(ethylene glycol) (PEG) counterparts. At present, zwitterionic materials have already been applied to a number of applications, including implantable medical devices, early cancer diagnostics, drug/gene delivery, antimicrobial coatings, and marine coatings.