If you are more of a visual person and would like to organize your folders and files using different colors, than check it out how to use color labels in Mac OS X.
The periodic table is a tabular arrangement of the chemical elements, organized on the basis of their atomic numbers, electron configurations (electron shell model), and recurring chemical properties.
If have been using Photoshop for a while now, you must had also notice the Mask Tool. But do you know what exactly it does and how and when should you decide to you use it?