The File menu is the primary means for loading molecules and other data into VMD. The built-in file readers will load molecular structures from combinations of topology files, coordinate files, and trajectory files. Readers are also included for data such as potential maps, electron density maps, Grasp surface data, and arbitrary 3-D geometric data from Raster3D scene files. VMD can load structures directly from Protein Data Bank over the internet, provided that a network connection is present. Entering the four-character PDB accession code in the molecule file broswer form will retrieve and load the structure over the network.