The Nobel Prize in Physiology or Medicine went to biophysicists Peter Hegemann of Humboldt University in Berlin and Georg Nagel of Julius-Maximilians-Universität Würzburg, along with neuroscientist Karl Deisseroth of Stanford University, for foundational work on optogenetics, a technology that uses light to activate specific cells such as neurons. Hegemann and Nagel discovered channelrhodopsin in the eye spot of the green alga Chlamydomonas; accounts differ on when that work began, with one source dating the discovery to the early 2000s and another placing the underlying research in the 1990s. Deisseroth inserted the channelrhodopsin gene into rat nerve cells and used blue light to control the movement of mice's whiskers. Abdel El Manira of the Karolinska Institute said the technology lets scientists link neural circuits to specific behaviors. Optogenetics has become a tool for studying or treating blindness, depression, and dementia, and is also applied to schizophrenia, anxiety, and addiction.

The Nobel Prize in Physics went to Francis Halzen of the University of Wisconsin-Madison for his contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos from beyond the solar system. IceCube is a cubic kilometer of ice threaded with sensors beneath the Antarctic ice sheet at the South Pole. Sources differ on its timeline: one says it was built between 2004 and 2011, another says only that it was completed in 2011. Within two years of completion, the observatory detected high-energy neutrinos of astrophysical origin. In 2018, researchers traced one such neutrino to a blazar, and in 2023 they produced the first map of the Milky Way built from neutrino data.

The Nobel Prize in Chemistry went to Henri Kagan and Kenso Soai for work on asymmetric synthesis, a chemical reaction that spontaneously produces only one mirror-image form, or enantiomer, of a chiral molecule. Kagan's institutional affiliation is identified variously as Université Paris-Saclay and as emeritus professor at the University of Paris-Sud. Soai is an emeritus professor at the Tokyo University of Science. Kagan is now 95 and Soai is 76.

Kagan reported in 1986 that manipulating a catalyst could produce a high proportion of one mirror-image form of a molecule. Soai's key finding, a chiral, self-replicating catalyst capable of amplifying that imbalance, is dated differently across accounts: one source places it nine years after Kagan's 1986 work, another gives 2003, and a third puts it generally in the 1990s. The scale of the amplification is also reported differently, with one account saying three repetitions of the reaction could increase an imbalance by 630,000 times, and another saying the effect took a starting imbalance of 0.00005% to a 99.5% preference for one form.

The research addresses homochirality, the puzzle of why life's building blocks occur overwhelmingly in one mirror-image form: amino acids are L-configured, while the sugars in DNA and RNA are D-configured. The prize committee and other sources point to the thalidomide tragedy of the 1950s, in which one enantiomer of the drug caused more than 10,000 birth defects in Europe, Canada and Australia, as a case for why distinguishing enantiomers matters in medicine. Ibuprofen, developed by Boots in the 1960s, contains an active S-form and an inactive R-form, though the body converts some of the inactive form into the active one. L-DOPA, used to treat Parkinson's disease, must be in its L-form to cross the blood-brain barrier; William Knowles solved that synthesis problem at Monsanto in the 1970s using chiral catalysts, work for which he won the Nobel Prize in Chemistry in 2001. Cells run on D-glucose for energy, while its mirror image, L-glucose, provides no calories but was judged financially unviable as a sweetener in the 1980s.

Kagan's work contributed to the development of the anti-HIV drug efavirenz, and Soai's research aids the synthesis of drugs such as levodopa for Parkinson's disease. Chirality also matters to the perfume industry. In 2001, France's science minister protested Kagan's omission from that year's Nobel Prize. Beyond medicine, chirality research is being explored for circularly polarized light displays, anti-counterfeiting security tags, and quantum electronics.