All organisms, regardless of whether they are single-celled or multi-celled, begin as one single cell. This initial cell is formed through the process of fertilization, where a sperm cell from the male combines with an egg cell from the female. This single cell, known as a zygote, then undergoes cell division and differentiation to form an entire organism with specialized cells and tissues. In some cases, such as certain bacteria and yeast, organisms can also reproduce asexually through cell division, where one parent cell divides into two daughter cells.
