Joe: By default LR keeps all of the history information, etc. solely in the database (catalogue). You can write this metadata out to the files one of two ways. One is to do it manually (select images and press Ctrl/Cmd-S as suggested), or by going to Metadata/Write metadata to files. The other way is to go into the LR preferences and check the box that says, "Autowrite changes to .xmp". It's off by default. Turning this one WILL cause a tradeoff in performance because every change to an image or images is then written to the files. Only you can decide if it's worth it. I leave it on for the same reason I have 'autobackup' set to 5 minutes in MS Word and other programs - because I'm lousy at remembering to save files. There's no 'save' feature in LR, but if your catalogue becomes corrupted and you've written the metadata out you can recover much faster because creating a new catalogue and importing images will bring MOST of the information with them. Collections, etc. are only in the catalogue.