Storage Cells

Storage Cells, are one of the core mechanics of storage in Applied Energistics 2, there are three kinds: one for items, one for fluids, and one for regions of space.

Item Storage

Item storage cells can hold up to 63 distinct types of items; the number of items they can store depends in part on how many types they're holding, and their storage capacity.
1k ME Item Storage Cell4k ME Item Storage Cell16k ME Item Storage Cell64k ME Item Storage Cell

Portable Item Storage

1k Portable Item Cell4k Portable Item Cell16k Portable Item Cell64k Portable Item Cell

Capacity Limits

Storage cells have limits of size, and limits of types, plus you need to consider the resource usage of your cells, to decide what your best options are. Each storage cell can store a fixed amount of data. Each type consumes a number of bytes (which varies with the cell size), and each item consumes one bit of storage, so eight items consume one byte, and a full stack of 64 consumes 8 bytes, regardless of how the item would stack outside an ME network. For instance, 64 identical saddles don't take up more space than 64 stone.
Gunning straight for top tier storage cells, is not generally the best idea, since you use more resources, but don't get any extra type storage.
Below is a table comparing the different tiers of storage cells, how much they store, and a rough estimate of their cost.

Storage Cell Contents Vs Cost

CellBytesTypesByte/TypeC-QuartzN-QuartzGoldDiamonds
1k ME Item Storage Cell1,0246385510
4k ME Item Storage Cell4,096633217530
16k ME Item Storage Cell16,38463128511091
64k ME Item Storage Cell65,5366351215320274

Storage Capacity with Varying Type Count

CellStacks of items With 1 Item In CellStacks of items With 63 Items in Cell
1k ME Item Storage Cell12765
4k ME Item Storage Cell508260
16k ME Item Storage Cell2,0321,040
64k ME Item Storage Cell8,1284,160

Fluid Storage

Spatial Storage