The Cell in Development and Inheritance, by Edmund Beecher Wilson, provided a textbook introduction to cell biology for generations of biologists in the twentieth century. In his book, Wilson integrated information about development, inheritance, chromosomes, organelles, and the structure and functions of cells. First published in 1896, the book started with 371 pages, grew to 483 pages in the second edition that appeared in 1900, and expanded to 1,231 pages by the third and final edition in 1925. Wilson dedicated the book to the cell biologist Theodor Boveri, whose work established the roles of chromosomes in cell division. With its explanations and many illustrations and diagrams, The Cell in Development and Inheritance enabled embryologists to better understand development in terms of cell structure and function.

Mitochondrial DNA (mtDNA) is located outside the nucleus in the liquid portion of the cell (cytoplasm) inside cellular organelles called Mitochondria. Mitochondria are located in all complex or eukaryotic cells, including plant, animal, fungi, and single celled protists, which contain their own mtDNA genome. In animals with a backbone, or vertebrates, mtDNA is a double stranded, circular molecule that forms a circular genome, which ranges in size from sixteen to eighteen kilo-base pairs, depending on species. Each mitochondrion in a cell can have multiple copies of the mtDNA genome. In humans, the mature egg cell, or oocyte, contains the highest number of mitochondria among human cells, ranging from 100,000 to 600,000 mitochondria per cell, but each mitochondrion contains only one copy of mtDNA. In human embryonic development, the number of mitochondria, the content of mtDNA in each mitochondrion, and the subsequent mtDNA activity affects the production of the oocytes, fertilization of the oocytes, and early embryonic growth and development.

All cells that have a nucleus, including plant, animal, fungal cells, and most single-celled protists, also have mitochondria. Mitochondria are particles called organelles found outside the nucleus in a cell's cytoplasm. The main function of mitochondria is to supply energy to the cell, and therefore to the organism. The theory for how mitochondria evolved, proposed by Lynn Margulis in the twentieth century, is that they were once free-living organisms. Around two billion years ago, mitochondria took up residence inside larger cells, in a process called endosymbiosis, becoming functional parts of those cells. Within each mitochondrion is the mitochondrial DNA (mtDNA), which is different from the DNA in the cell's nucleus (nDNA). Organisms inherit their mitochondria only from their mothers via egg cells (oocytes). Mitochondria contribute to the development of oocytes, the release of the oocyte from the ovary (ovulation), the union of oocyte and sperm (fertilization), all stages of embryo formation (embryogenesis), and growth of the embryo after fertilization.

Mitochondrial diseases in humans result when the small organelles called mitochondria, which exist in all human cells, fail to function normally. The mitochondria contain their own mitochondrial DNA (mtDNA) separate from the cell's nuclear DNA (nDNA). The main function of mitochondria is to produce energy for the cell. They also function in a diverse set of mechanisms such as calcium hemostasis, cell signaling, regulation of programmed cell death (apoptosis), and biosynthesis of heme proteins that carry oxygen. When mitochondria fail to fulfill those functions properly in the cell, many different maladies, including death, can occur. Humans inherit mitochondria from the mother through the egg cell, and all the mtDNA molecules in a person are identical to each other. But the mutation rate is much higher in the mtDNA than in nuclear DNA, and some individuals may have more than one type of mtDNA. As egg cells develop, they divide via a process called meiosis. As egg cells divide, mitochondria of different types can randomly segregate in some new cells but not in others. As a result, two offspring from the same female might differ in their types of mitochondria. Random amounts of the two mitochondria types can lead to some offspring inheriting a mitochondrial disease or developmental abnormalities while others are normal.

Mitochondria are organelles found in the cytoplasm of eukaryotic cells. They are composed of an outer membrane and an inner membrane. The outer membrane faces the cellular cytoplasm, while the inner membrane folds back on itself multiple times, forming inner folds, called cristae. The space between the two membrane layers is called the intermembrane space, and the space within the inner membrane is called the matrix.

Chloroplasts are the organelles in plant and algal cells that conduct photosynthesis. A single chloroplast has an outer membrane and an inner membrane, with an intermembrane space in between. Within the inner membrane, interconnected stacks of thylakoids, called granum, float in a protein rich fluid called the stroma. These thylakoid stacks contain chlorophyll, a pigment which converts sunlight into usable energy for plants and free oxygen from water. The stacks are sites of light reactions within a plant cell.