The *.veg files are the vegetations itself (trees, plants, flowers) and were created with the SolidGrowth system proper to Vue d'Esprit and the powerful and envyed secret of e-onsoftware.com. *.mat files are the materials applied to truncs, leaves, flowers (and in other folders for all the materials). You can try to use, i.e. a *.mat file from 1 plant on another. Try it, you will be surprised! The *.prv file (vegetation.prv or object.prv etc.) are the files what allows you to see the preview thumbnails in the plants or object or material browsers. If you delete this one, Vue will create immediately a new one. Do not try to delete other files. You will have to re-install Vue if you do so. To create your own grass, trees, plants, you need to own a program what can do it. X-frog especially for plants or any modeler. Audity has created a great grass patch (in the Vue free stuff). Only he can tell you what program he used for it. Guitta