ahh yes ... OK... DPI stands for Dots Per Inch, and what that number means is pretty self-explanatory. It tells you how many dots will appear on a given line in an inch of space. So, the higher the number the more dots which means better resolution. Another important measurement to know if you decide to get into printing would be LPI (or Lines Per Inch). That number tell you how many lines will appear in an inch. I think the standard for that is 150, but someone who knows more about printing should correct me of I am wrong. As far as what tasquah is talking about I agree. When you are working on your image you should start smaller than what you want in the end. Otherwise it will take bloody forever to render 1600x1600@300DPI just to see if the hair looks right or whatever. Something to keep in mind would be to set up your document to have the same aspect ratio (i.e. 4:3, or 640x480) so when you do go for the final large render it will look the same (only bigger) as what you worked on. Hope that helps