The numerical equality of paternal and maternal chromosomes at fertilization was established by Theodor Boveri and Jean-Louis-Léon Guignard.

Herman Hollerith designs tabulating machines for 1890 U.S. Census

Hypertext Pioneer Vannevar Bush Is Born

US Census Bureau announces results using Herman Hollerith's machine

Gabriel Lippmann announces a "method of reproducing colors photographically based on the phenomenon of interference".

William Kennedy Laurie Dickson develops the "kinetoscopic" motion picture camera while working for Thomas Edison.

Publication of August Weismann's book Das Keimplasma (The Germ Plasm) emphasized meiosis as an exact mechanism of chromosome distribution.

Joseph Whiteaves describes Anomalocaris, meaning "anomalous shrimp," from the Cambrian. The fossil that Whiteaves identifies as a shrimp will later prove to be part of a much larger animal.

Entomologist E.B. Poulton studies caterpillars from the species Gastropacha quercifolia, noting how siblings look different depending on where they live and what they eat. His discovery will become known as phenotypic plasticity.

Wilhelm Wien discovers that the maximum wavelength emitted by hot body varies inversely with its absolute temperature. Wien's law becomes useful in establishing the temperature of stars. The problems he has with deriving an equation to describe black-body radiation lead to Max Planck's introduction of the quantum in 1900.

Hans Driesch expounded the view that all nuclei of an organism were equipotential but varied in their activity in accordance with the differentiation of tissues.

Karl Pearson published the first in a long series of contributions to the mathematical theory of evolution. Methods for analyzing statistical frequency distributions were developed in detail.

William Bateson's Materials for the Study of Variation emphasized the importance of discontinuous variations, foreshadowing the rediscovery of Mendel's work.

Eugène Dubois publishes his monograph of Pithecanthropus erectus, or Java Man, a missing link between humans and apes.

French paleontologist Charles Brongniart describes a fossil dragonfly from the Carboniferous with a 2-foot (63-centimeter) wingspan. The find implies a higher oxygen content in the Earth's ancient atmosphere.

The intricately carved mammoth ivory figurine known as the Lady (or Venus) of Brassempouy is discovered in France. At roughly 25,000 years old, it ranks among the earliest known depictions of a human face.

Joseph John (J.J.) Thomson announces that he has found that the velocity of cathode rays is much lower than that of light.

A team of paleontologists, including Samuel Williston, Elmer Riggs and Barnum Brown, successfully excavates a Triceratops fossil in Wyoming.

Charles Thomson Rees Wilson develops the CLOUD CHAMBER, a box containing a gas that is saturated. When a charged particle passes through the gas, small droplets are formed that make the track of the particle visible. The cloud chamber becomes a powerful tool in particle physics.

Pierre Curie shows that as the temperature of the magnet is increased, there is a level at which the magnetism is disrupted and ceases to exist. This temperature is still called the Curie point.

Wilhelm Konrad Röntgen (Roentgen) discovers X-rays, which will soon be applied in the visualization of bodily structures and in the induction of genetic mutations (both intentionally and accidentally).

Auguste and Louis Lumi re invent the cin matographe.

Cornflakes are invented in Battle Creek, Michigan, by John Harvey Kellogg — the chief medical officer of the Battle Creek sanitarium.

E. B. Wilson publishes The Cell in Development and Heredity. This influential treatise (ultimately reprinted in several editions) distills the information compiled concerning cytology in the half-century since Schleiden and Schwann put forth the cell theory.

Dublin anatomist Daniel Cunningham concludes that Neanderthals represent an intermediate step between Pithecanthropus erectus and modern humans.

J. de Morgan describes nine pierced fossil urchins found in a Chalcolithic tomb at Toukh.

Less than three months after the discovery of x-rays, Dartmouth College Professor of Physics Edwin Frost and his brother, the then physician in chief of Mary Hitchcock Hospital, Gilman Frost, MD, take the first clinical X-ray in the US — an image of Eddie McCarthy's fractured left wrist.

Antoine-Henri Becquerel discovers rays produced by uranium — the first observation of natural radioactivity.

Gabriel Bertrand coined the term COENZYME to designate inorganic substances which were necessary to activate certain enzymes.

Renowned physicist Lord Kelvin gives a lecture at London's Victoria Institute claiming that the sun, which is cooling from its initial formation, can be no more than 20 million years old.

Joseph John Thomson discovers the electron, the first known particle that is smaller than an atom, in part because he has better vacuum pumps that were previously available. He, and independently, Emil Wiechert, determine the ratio of mass to charge of the particles by deflecting them by electric and magnetic fields.

Marie Curie begins research of "uranium rays" that will lead to the discovery of radioactivity.

America's first subway opens, in Boston.

Russian physicist Alexander Popov uses an antenna to transmit radio waves over a distance of 5 km.

Marie and Pierre Curie discovered that thorium, gives off "uranium rays", which Marie renames RADIOACTIVITY.

Kodak introduces the Folding Pocket Kodak.

British physicist Ernest Rutherford discovers the radioactivity from uranium has at least two different forms, which he calls alpha and beta rays.

Fritz Geisel, Antoine-Henri Becquerel, and Marie Curie proved the beta rays consist of high-speed electrons.

L. Cuénot (France) working with animals, and Strasburger (Germany) working with plants, advance theory that sex is controlled within the germ cell, not by environment.

Richard Altmann renames "nuclein" as NUCLEIC ACID.

The First International Congress of Genetics held in London.

William Bateson writes a paper on hybridisation and cross-breeding as a method of scientific investigation that anticipates Mendel's rediscovery.