The Crystallography and NMR System (CNS) version 1.2 has been released, offering improved tools for crystallographic and NMR structure determination. CNS provides a flexible framework for exploring new methods, solving complex structures, and analyzing macromolecular dynamics. Version 1.2 includes an enhanced bulk solvent model for crystallographic refinement, which uses a combined grid search and least-squares optimization to improve robustness and reduce R values, especially at lower resolutions. It also allows thermal factor sharpening of electron density maps, enhancing resolution details while minimizing noise. The bulk solvent model in CNS accurately represents the interface between the crystal lattice and the protein, using a mask to distinguish solvent and macromolecular regions. This model is crucial for refining macromolecular structures, as it accounts for the solvent's effect on electron density. The new solvent model is more robust and efficient, with optimized parameters for high and low-resolution structures. Thermal factor sharpening enhances low-resolution maps by applying a negative B-factor value in a resolution-dependent weighting scheme, increasing detail in high-resolution features while managing noise. This technique is particularly useful when experimental phase information is available, as it improves the quality of electron density maps. CNS 1.2 includes new modules and task files for bulk solvent optimization and thermal factor sharpening, with no changes to the source code. These updates allow for more accurate and efficient structure refinement. The system supports various data formats and is compatible with multiple operating systems, including Linux, Mac OS X, and Windows. The CNS website provides task files, parameter files, and module files for structure determination, along with documentation and tutorials. Users can modify task files and set default parameters for structure refinement and electron density map calculations. The system is designed for modular, flexible computation, enabling the development of new algorithms and precise modification of existing ones without requiring source code changes. CNS 1.2 includes numerous improvements, such as enhanced bulk solvent modeling, thermal factor sharpening, and optimized parameter settings. These features improve the accuracy and efficiency of structure determination, making CNS a powerful tool for structural biology research.The Crystallography and NMR System (CNS) version 1.2 has been released, offering improved tools for crystallographic and NMR structure determination. CNS provides a flexible framework for exploring new methods, solving complex structures, and analyzing macromolecular dynamics. Version 1.2 includes an enhanced bulk solvent model for crystallographic refinement, which uses a combined grid search and least-squares optimization to improve robustness and reduce R values, especially at lower resolutions. It also allows thermal factor sharpening of electron density maps, enhancing resolution details while minimizing noise. The bulk solvent model in CNS accurately represents the interface between the crystal lattice and the protein, using a mask to distinguish solvent and macromolecular regions. This model is crucial for refining macromolecular structures, as it accounts for the solvent's effect on electron density. The new solvent model is more robust and efficient, with optimized parameters for high and low-resolution structures. Thermal factor sharpening enhances low-resolution maps by applying a negative B-factor value in a resolution-dependent weighting scheme, increasing detail in high-resolution features while managing noise. This technique is particularly useful when experimental phase information is available, as it improves the quality of electron density maps. CNS 1.2 includes new modules and task files for bulk solvent optimization and thermal factor sharpening, with no changes to the source code. These updates allow for more accurate and efficient structure refinement. The system supports various data formats and is compatible with multiple operating systems, including Linux, Mac OS X, and Windows. The CNS website provides task files, parameter files, and module files for structure determination, along with documentation and tutorials. Users can modify task files and set default parameters for structure refinement and electron density map calculations. The system is designed for modular, flexible computation, enabling the development of new algorithms and precise modification of existing ones without requiring source code changes. CNS 1.2 includes numerous improvements, such as enhanced bulk solvent modeling, thermal factor sharpening, and optimized parameter settings. These features improve the accuracy and efficiency of structure determination, making CNS a powerful tool for structural biology research.