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.
From the Latin word for womb (in turn from mater or mother), a matrix is either the intercellular substance of a tissue, the material in which a fossil is embedded, or a mold from which a relief surface is made in printing or phonograph manufacturing.he hero, Case, jacks in to the matrix through wiring that is (perhaps, since it's not entirely clear) integrated with his brain and explores the matrix with a deck or computer console that provides a holographic view.