1.   In its skin are cells called chromatophores, and each has little sacs of red, black and yellow pigments.

2.   It grows in the ovary inside a little sac which feeds the developing ovum.

3.   Retroviruses, little sacs of genetic material, put out a kind of reverse code or defective blueprint causing cell overgrowth.

4.   The total surface of area of those little sacs, where blood capillaries exchange oxygen for carbon dioxide, is roughly the same as that of a tennis court.

5.   We breathe air into lungs elaborated with little sacs called alveoli.