An array of cellular organelles is seen through the nuclear envelope in this view from within the nucleus. The nuclear contents themselves are not shown. Although the nuclei of many cells are round, those of neutrophils are characteristically irregular in shape, pinched into several discrete lobes. In the image above, three lobes of this cell's nucleus may be seen extending to the left, upper left and at right.The nucleus is the repository for most of the cell's genes, encoded onto strands of DNA: long rope-like molecules capable of storing vast quantities of information. In addition to their importance in heredity, genes direct the cell in its everyday metabolism and in responses to environmental conditions. Human cells contain some 25,000 genes, although not all of these are needed by every cell. Because the mature neutrophil does not reproduce and has a limited lifespan (only a few days!), most of its genes are packed away in the nucleus unused. Nonetheless, though the entire cell measures less than a thousandth of an inch in size, its DNA, if stretched out & unraveled, would be several feet in length!