Title: Werner Heisenberg
Content:  Werner Karl Heisenberg (5 December 1901 – 1 February 1976) was a German theoretical physicist and one of the key pioneers of quantum mechanics. He published his work in 1925 in a breakthrough paper. In the subsequent series of papers with Max Born and Pascual Jordan, during the same year, this matrix formulation of quantum mechanics was substantially elaborated. He is known for the uncertainty principle, which he published in 1927. Heisenberg was awarded the 1932 Nobel Prize in Physics "for the creation of quantum mechanics". Heisenberg also made important contributions to the theories of the hydrodynamics of turbulent flows, the atomic nucleus, ferromagnetism, cosmic rays, and subatomic particles. He was a principal scientist in the German 
Title: History of chemistry
Content:  quantum theory made Schrödinger and several other physicists profoundly unhappy, and he devoted much of his later life to formulating philosophical objections to the generally accepted interpretation of the theory that he had done so much to create.) German theoretical physicist Werner Heisenberg was one of the key creators of quantum mechanics. In 1925, Heisenberg discovered a way to formulate quantum mechanics in terms of matrices. For that discovery, he was awarded the Nobel Prize for Physics for 1932. In 1927 he published his uncertainty principle, upon which he built his philosophy and for which he is best known. Heisenberg 
Title: Werner Heisenberg
Content:  as a university lecturer and assistant to Bohr in Copenhagen. It was in Copenhagen, in 1927, that Heisenberg developed his uncertainty principle, while working on the mathematical foundations of quantum mechanics. On 23 February, Heisenberg wrote a letter to fellow physicist Wolfgang Pauli, in which he first described his new principle. In his paper on the principle, Heisenberg used the word "Ungenauigkeit" (imprecision), not uncertainty, to describe it. In 1927, Heisenberg was appointed ordentlicher Professor (professor ordinarius) of theoretical physics and head of the department of physics at the University of Leipzig; he gave his inaugural lecture there on 1 February 1928. In his first paper published from Leipzig, Heisenberg used the Pauli exclusion principle 
Title: The Physical Principles of the Quantum Theory
Content:  Werner Heisenberg (b. 1901 - d. 1976) was a renowned German theoretical physicist whose work pioneered and advanced quantum mechanics. He received his PhD in 1923 from Ludwig Maximilian University of Munich under Arnold Sommerfeld. He was awarded the 1932 Nobel Prize in Physics "for the creation of quantum mechanics, the application of which has led to the discovery of the allotropic forms of hydrogen".
Title: Uncertainty (book)
Content:  the German nuclear weapons program during World War II. He received his doctorate degree at 22, just two years prior to his introduction of matrix mechanics. After being appointed professor theoretical physics at the University of Leipzig in 1926, Heisenberg published his uncertainty principle in 1927 and went on to win the 1932 Nobel Prize at the age of 32. The book draws its name from the uncertainty principle, which states that, in quantum mechanics, there exists pairs of quantities, such as position and velocity, in which you cannot know the precise value of both at the same time. Heisenberg was sympathetic to the Third Reich, though he never joined the Nazi Party.
Title: Werner Heisenberg
Content:  From 1924 to 1927, Heisenberg was a Privatdozent at Göttingen, meaning he was qualified to teach and examine independently, without having a chair. From 17 September 1924 to 1 May 1925, under an International Education Board Rockefeller Foundation fellowship, Heisenberg went to do research with Niels Bohr, director of the Institute of Theoretical Physics at the University of Copenhagen. His seminal paper, "Über quantentheoretische Umdeutung kinematischer und mechanischer Beziehungen" ("Quantum theoretical re-interpretation of kinematic and mechanical relations"), was published in September 1925. He returned to Göttingen and, with Max Born and Pascual Jordan over a period of about six months, developed the matrix mechanics formulation of quantum mechanics. On 1 May 1926, Heisenberg began his 
Title: Jochen Heisenberg
Content:  Jochen Heisenberg (born 16 May 1939) is a German physicist specializing in nuclear physics, and Professor Emeritus of Physics at the University of New Hampshire. He is the son of Nobel Prize-winning physicist Werner Heisenberg, who was a co-founder of the quantum mechanics, and who, in particular, introduced the uncertainty principle. He is the brother of German neurobiologist and geneticist Martin Heisenberg and the uncle of film director Benjamin Heisenberg.
Title: Werner Heisenberg
Content:  Heisenberg's paper establishing quantum mechanics has puzzled physicists and historians. His methods assume that the reader is familiar with Kramers-Heisenberg transition probability calculations. The main new idea, non-commuting matrices, is justified only by a rejection of unobservable quantities. It introduces the non-commutative multiplication of matrices by physical reasoning, based on the correspondence principle, despite the fact that Heisenberg was not then familiar with the mathematical theory of matrices. The path leading to these results has been reconstructed in MacKinnon, 1977, and the detailed calculations are worked out in Aitchison et al. In Copenhagen, Heisenberg and Hans Kramers collaborated on a paper on dispersion, or 
Title: Heisenberg's entryway to matrix mechanics
Content:  One of Heisenberg's seniors, Max Born explained how he took his strange "recipe" given above and discovered something ground breaking: "By consideration of ...examples...[Heisenberg] found this rule.... This was in the summer of 1925. Heisenberg...took leave of absence...and handed over his paper to me for publication....""Heisenberg's rule of multiplication left me no peace, and after a week of intensive thought and trial, I suddenly remembered an algebraic theory....Such quadratic arrays are quite familiar to mathematicians and are called matrices, in association with a definite rule of multiplication. I applied this rule to Heisenberg's quantum condition and found that it agreed for the diagonal elements. It was easy to guess what 
Title: Measurement in quantum mechanics
Content:  A 1925 paper by Heisenberg, known in English as "Quantum theoretical re-interpretation of kinematic and mechanical relations", marked a pivotal moment in the maturation of quantum physics. Heisenberg sought to develop a theory of atomic phenomena that relied only on "observable" quantities. At the time, and in contrast with the later standard presentation of quantum mechanics, Heisenberg did not regard the position of an electron bound within an atom as "observable". Instead, his principal quantities of interest were the frequencies of light emitted or absorbed by atoms. The uncertainty principle dates to this period. It is frequently attributed to Heisenberg, who introduced the concept in analyzing a thought experiment where one attempts to measure an electron's position and momentum simultaneously. However, Heisenberg did not give precise mathematical definitions of what the "uncertainty" in these measurements meant. The precise mathematical statement of the position-momentum uncertainty principle is due to Kennard, Pauli, and Weyl, and its generalization to arbitrary pairs of noncommuting observables is due to Robertson and Schrödinger. Writing, an expression first postulated by Max Born in 1925, recovers the Kennard–Pauli–Weyl statement of the uncertainty principle.

Question: what did werner heisenberg discover?
Answer: Matrix mechanics.