Shoukhrat Mitalipov, Masahito Tachibana, and their team of researchers replaced the mitochondrial genes of primate embryonic stem cells via spindle transfer. Spindle replacement, also called spindle transfer, is the process of removing the genetic material found in the nucleus of one egg cell, or oocyte, and placing it in another egg that had its nucleus removed. Mitochondria are organelles found in all cells and contain some of the cell’s genetic material. Mutations in the mitochondrial DNA can lead to neurodegenerative and muscle diseases. Mitalipov and Tachibana used spindle replacement to produce healthy offspring from an egg with mutated mitochondria in rhesus macaques (Macaca mulatta). The experiment showed that spindle transfer eliminated the chance of transmission of mitochondrial diseases from the affected primates to their offspring, offering the potential to eliminate mitochondrial diseases in humans.

Between 1958 and 1962, physicians Olive W. Smith, George V. Smith, and Robert W. Kistner performed experiments that demonstrated the effects of the drugs MER-25 and clomiphene citrate on the female human body. MER-25 and clomiphene citrate are drugs that affect estrogen production in women. At the time of the experiment, researchers did not know which organ or organs the drugs affected, the ovaries and/or the anterior pituitary gland. To determine that, the physicians reviewed nine of their own previous studies in women in which they measured the urinary output of hormones after the administration of either drug. Based on their examination the researchers concluded that MER-25 appeared to influence the anterior pituitary gland in the brain to produce a response in the ovaries and that clomiphene citrate appeared to act on the ovaries. Their results provided early evidence about the mechanisms of both drugs. Later, clomiphene citrate became a common fertility drug.

In 1963, Ignacio Ponseti and Eugene Smoley experimentally determined an effective and minimally invasive method of treating congenital clubfoot. Congenital clubfoot is a disorder in which a newborn’s foot is rigidly turned inwards and upwards. During the early 1960s, orthopedists often relied on invasive surgical procedures to treat clubfoot. In Ponseti and Smoley’s experiment, Ponseti and Smoley had a team of physicians treat patients with clubfoot using the Ponseti method, which consisted of manually manipulating each patient’s foot into a more desirable position and subsequently casting each foot to heal in place. After following up with the patients for several years, Ponseti and Smoley concluded that the Ponseti method is an effective alternative to the more invasive surgical procedures that orthopedists had often relied on. Ponseti and Smoley provided physicians with a novel and minimally invasive method of correcting foot deformities to ensure that developing infants maintain healthy feet.

During 1964, David Hubel and Torsten Wiesel studied the short and long term effects of depriving kittens of vision in one eye. In their experiments, Wiesel and Hubel used kittens as models for human children. Hubel and Wiesel researched whether the impairment of vision in one eye could be repaired or not and whether such impairments would impact vision later on in life. The researchers sewed one eye of a kitten shut for varying periods of time. They found that when vision impairments occurred to the kittens right after birth, their vision was significantly affected later on in life, as the cells that were responsible for processing visual information redistributed to favor the unimpaired eye. Hubel and Wiesel worked together for over twenty years and received the 1981 Nobel Prize for Physiology or Medicine for their research on the critical period for mammalian visual system development. Hubel and Wiesel’s experiments with kittens showed that there is a critical period during which the visual system develops in mammals, and it also showed that any impairment of that system during that time will affect the lifelong vision of a mammal.

In the 1950s and 1960s, Roger Sperry performed experiments on cats, monkeys, and humans to study functional differences between the two hemispheres of the brain in the United States. To do so he studied the corpus callosum, which is a large bundle of neurons that connects the two hemispheres of the brain. Sperry severed the corpus callosum in cats and monkeys to study the function of each side of the brain. He found that if hemispheres were not connected, they functioned independently of one another, which he called a split-brain. The split-brain enabled animals to memorize double the information. Later, Sperry tested the same idea in humans with their corpus callosum severed as treatment for epilepsy, a seizure disorder. He found that the hemispheres in human brains had different functions. The left hemisphere interpreted language but not the right. Sperry shared the Nobel Prize in Physiology or Medicine in 1981for his split-brain research.

From February 2003 to December 2010, researchers of the Management of Myelomeningocele Study, or MOMS, clinical trial compared the safety and efficacy of different treatments for a specific type of spina bifida, called myelomeningocele. Myelomeningocele, the most frequent and severe form of spina bifida, is a condition in which the bony spinal column does not develop correctly, which causes an opening of the spine, exposure of the spinal cord, and formation of a small sac containing cerebrospinal fluid. Myelomeningocele affects 3.4 infants per 10,000 live births in the United States and is fatal in ten percent of affected infants. Investigators in the MOMS trial aimed to find a more successful treatment for myelomeningocele through different types of surgery. To accomplish that, they performed prenatal, or in utero, and postnatal repair operations in their study. The MOMS researchers concluded that prenatal repair improved motor and neurologic outcomes, such as the ability to activate and coordinate the muscles and limbs, and reduced the risk for fetal death.

From 1951 to 2001, researchers at the University of Oxford in Oxford, England, conducted the British Doctors’ Study, a study that examined the smoking habits, disease rates, and mortality rates of physicians in Britain. Two epidemiologists, scientists who study occurrence and distribution of disease, Richard Doll and Austin Bradford Hill, initiated the study, and statistician Richard Peto joined the team in 1971. The objective of the study was to assess the risks associated with tobacco use, and its relationship to lung cancer. The researchers tracked 34,439 male doctors practicing in Britain, and recorded smoking habits, development of diseases including lung cancer, other cancers, respiratory diseases, cardiovascular diseases, and mortality rates. The researchers published updated results every ten years. In 1980, Doll and other researchers concluded a related study on the smoking habits and disease rates of female doctors practicing in Britain. The results of both studies provided evidence that individuals who smoked tobacco were more likely to develop chronic respiratory illnesses, including lung cancer, and cardiovascular diseases.

"A Diffusible Agent of Mouse Sarcoma, Producing Hyperplasia of Sympathetic Ganglia and Hyperneurotization of Viscera in the Chick Embryo," by Rita Levi-Montalcini and Viktor Hamburger, appeared in 1953 in the Journal of Experimental Zoology. The paper provided the first evidence that nerve growth factor is a diffusible substance. Nerve growth promoting tumors were implanted into developing embryos to determine whether the tumors stimulated growth by direct contact or by a diffusible substance. The tumors were implanted into different parts of the embryo; one set of experiments implanted the tumor directly in the embryo, while another set of experiments placed the tumor on an exterior membrane. The membrane provided a barrier to direct contact with the nervous system, and allowed some chemical interaction between the tumor and the embryo. The tumor stimulated growth in both orientations, demonstrating that nerve growth factor was a chemical agent. The paper ends with two possible conclusions for the mechanism of nerve growth, the tumor may have been directly stimulating the ganglia by a diffusible signal, or it may have reduced the resistance of the chick tissues to the nerve growth. The term "nerve growth factor" is not explicitly used in this paper, and is referred to as a "diffusible agent" or a "growth promoting agent."

Alejandro Sánchez Alvarado's laboratory group has employed molecular tools to investigate old questions about regeneration and as a result have identified some of the molecular mechanisms determining polarity. Recent work by his group has shown Wnt-β-catenin signaling determines whether a tail or a head will form during regeneration in planarians. This study was motivated by work Thomas Hunt Morgan conducted in the late nineteenth century. Morgan observed that during regeneration a planarian cut into rather small pieces would sometimes regenerate a head at both its anterior and posterior end rather than a head and a tail. This led Morgan to think the size of the piece must affect the regenerative process.

On 10 March 1988, China's first baby conceived through human in vitro fertilization (IVF) and embryo transfer (ET), commonly referred to as a test-tube baby, was born at the Peking Hospital (PUTH) in Beijing. This birth was reported in numerous media reports as a huge step forward in China's long march to keep pace with global advances in science and technology. Led by gynecologist Zhang Lizhu, the PUTH research team had devoted more than four years to the human IVF-ET project. The team had to start by learning the basics of human egg morphology and embryology in order to design an IVF-ET strategy that was suited to the reproductive pathology affecting China's infertile population.