Opening 3DM files, which are commonly used for 3D modeling and CAD software, can be done using various applications. One of the most popular applications for opening 3DM files is Rhinoceros 3D (Rhino), which is a commercial 3D computer graphics and computer-aided design (CAD) software. Another option is using Autodesk Fusion 360, a cloud-based 3D CAD, CAM, and CAE platform for product development. Additionally, some other 3D modeling software like AutoCAD, SolidWorks, and SketchUp also have the capability to open 3DM files. If you don't have access to these specific software, you can also use online file converters and viewers to open 3DM files. Websites like Online 3D Viewer and ConvertCADFiles offer free services to upload and view 3DM files online. In conclusion, opening 3DM files is a straightforward process when using the right software or online tools, and understanding which application is best for your specific needs will help streamline the process of working with 3DM files.