Human cells come in a wide variety of shapes and sizes. The mass of an average human cell is about
2×10
−11
grams. Red blood cells are one of the smallest types of cells with a volume of approximately
1×10
−6
meters
3
. Biologist have recently discovered that the density of some types of cells can indicate the presence of disorders such as sickle cell anemia or leukemia. Density is calculated as
volume
mass
​
.