3D and 4D images – stacks and hyperstacks

Digital images are not only bidimensional (2D) or multichannel (2D with several channels). We may have several 2D images with spatial, temporal, or any kind of relationship between them. These kinds of images are managed by ImageJ as stacks and hyperstacks. Stacks have three spatial dimensions: x, y, and z. Hyperstacks have four dimensions (x, y, z, and time) and both may also have several channels. As you may be thinking, these two kinds of images are really powerful, since almost any kind of single experiment that provides image results which are somehow related can be handled with them. Now, every image position is not a pixel but a voxel (it has volume), and has three or more dimensions. There is no need that all the dimensions are different from one, and consequently stacks are a subgroup of hyperstacks.

Let's open one sample stack to start familiarizing with this concept. Open the sample image described as T1 head (file t1-head.zip). This stack...