First of all, an optical drive can be a CD, DVD, or BluRay drive. The button isn't invisible, it's just hidden in plain site by design. The previous pictures show its location, but here is one more. This is a picture of the top of a 660 showing 2 drives.
What is difference between an osteon and osteocyte? An osteon is the functional unit of cortical bone. Osteons contain osteocytes, which are cells that produce bone matrix.
In general, a matrix is the place where something develops. For instance, the nail matrix is where the nail develops. Alternatively, it is a mechanism for harvesting electriciâ¦ty from an organism while creating a virtual reality envornment to keep the organism oblivious to its metareality.