All living things are made up of cells. some organisms, such as bacteria, exist only as single-celled organisms. others, consist of countless cells all working together to form a single living being. humans are comprised of trillions of cells that are organized into tissues such as muscle and skin or organs like the liver and lungs. every organic life form starts from a single cell. cells form a tissue, tissues form an organ and organs form the human body. these cell divisions by which a single cell divides a hundred trillion times is a process called growth. it is a unique and very complex process that happens in the body. a normal cell follows a uniform life cycle and reproduction. the abnormal (mutant) cells are cancer cells. cancer cells happens when a certain cell (dna) gets a different signal that causes mutation. when a cell senses a mistake, the system eliminates (self destructs) itself from the body, however, there are some instances that a cell’s mutation is left undetected. these cells reproduce and grow in a manner that is not even or regular in pattern or movement; hence, the growth of the cancers cells. cancer cells vary from normal cells. they have different characteristics that allowed researchers to understand cell mutation extensively. all normal cells carry characteristics that are essential to perform a normal bodily function. these cells differ in shape and size but they are uniformed depending on what type of cells they are. all human cells are eukaryotic (any organism having as it fundamental structural unit a cell type that contains specialized organelles in the cytoplasm, a membrane-bound nucleus enclosing genetic material organized into chromosomes, and an elaborate system of division by mitosis or meiosis, characteristic of all life forms except bacteria, blue-green algae, and other primitive microorganisms) because they contain a true nucleus that can hold genetic information, like dna (deoxyribonucleic acid) and rna (ribonucleic acid). these genes are responsible for all cellular activities and functioning. healthy cells divide in an orderly manner to produce more cells only when the body needs them. they follow the lifecycle which includes mitosis (the usual method of cell division, characterized typically by the resolving of the chromatin of the nucleus into a threadlike form, which condenses into chromosomes, each of which separates longitudinally into two parts, one part of each chromosome being retained in each of two new cells resulting from the original cell), meiosis (part of the process of gamete formation, consisting of chromosome conjugation and two cell divisions, in the course of which the diploid chromosome number becomes reduced to the haploid), and apoptosis ( the death of a cell).