MAIN is a computer program dealing with computational aspects of macromolecular structure determination used the areas of macromolecular crystallography and electron microscopy. It is usually run through an interactive interface. With MAIN a user can

• visualize molecular models and electron density maps using a 3D graphics interface,
• build and rebuilding molecular structures using automated and manual tools,
• modify electron density maps (solvent flattening and flipping, envelopes manipulation, averaging, filtering noise),
• refine structures using real and reciprocal space targets,
• analyze and validate structural models