Chromosomes are found in the nucleus of a cell.
Chromosomes have various shapes and lengths, but each species has a specific pattern of chromosomes.
For example, humans have 46 chromosomes, which are very small. Though very small, human chromosomes may be seen clearly through a microscope when they are stained with dyes. One problem in examining chromosomes is that they show up only when cells divide. Staining is done after fixed cells are distributed on a glass. The resulting abnormalities in the chromosomes are called aberrations.