Inside a cell. Panoramic view from inside an imaginary cell. The densely folded endoplasmic reticulum, a membrane that divides the cell into compartments, is shown in yellow and red. The nucleus, covered with nuclear pores, can be seen at lower right through a tear in the membrane. The violet spheres are secretory vesicles produced by the golgi apparatus (violet, centre). These vesicles carry substances such as enzymes and hormones out of the cell. A mitochondrion (with red inner membranes) is seen at centre right.