This chapter explains the different tools that can be used for creating composite photographs as well as the intricacies of working with layers, channels, mask channels and pen paths. To begin with, let the reader focus on some of the basic principles such as how to make a selection and the interrelationship between selections, alpha channels, masks and the quick mask mode. The marching ants indicate the extent of an active selection and any image modifications the people carry out are applied within the selected area only. Photoshop gets round this problem by antialiasing the edges, which means filling the gaps with in-between tonal values so that non-vertical/horizontal sharp edges are rendered smoother by the anti-aliasing process. Layer masks and vector masks are linked by default to the layer content and if the people move a masked layer or transform the layer content, the mask is adjusted along with it (as long as no selection is active).