…hollow disks that are called thylakoids (“saclike”). The chloroplasts of most higher plants have regions, called grana, in which the thylakoids are very tightly stacked. When viewed by electron microscopy at an oblique angle, the grana appear as stacks of disks. When viewed in cross section, it is apparent that…

…form membrane-bounded closed sacs (thylakoids) often arranged in stacks (grana). Solar energy splits two molecules of H2O into molecular oxygen (O2), four protons (H+), and four electrons.

…to hollow sacklike disks called thylakoids. Stacks of thylakoids embedded with pigment molecules are called grana. The inner matrix of the chloroplast is called the stroma.