• The connective tissue capsule that covers the gland.
• The adrenal cortex, which has layers of cells in three groups (each a “zona”) with distinct arrangements and staining.
• The medulla, which consists primarily of one type of cell and is more darkly stained.

Because of its endocrine functions, the adrenal has numerous blood vessels.

• Click for a detailed image of the cortex and medulla.

See this slide with the virtual microscope

I don't see the virtual slide, I must need the download.