Leonor Michaelis (16 January 1875 – 8 October 1949) was a German biochemist, physical chemist, and physician.

Leonor Michaelis was born in Berlin, Germany, on 16 January 1875 to Jewish parents Hulda and Moritz [1] .

Michaelis graduated from the humanistic Köllnisches Gymnasium in 1893 after passing the Abiturienten Examen.

It was during that time that Michaelis's interest in physics and chemistry was first sparked as he was encouraged by his teachers to utilize the relatively unused laboratories at his school.

[citation needed] With concerns about the financial stability of a pure scientist, he commenced his study of medicine at Berlin University in 1893.

During his time at Berlin University, Michaelis worked in the lab of Oscar Hertwig, even receiving a prize for a paper on the histology of milk secretion.

Michaelis's doctoral thesis work on cleavage determination in frog eggs led him to write a textbook on embryology.

He passed his physician's examination in 1896 in Freiburg, and then moved to Berlin, where he received his doctorate in 1897.

After receiving his medical degree, Michaelis worked as a private research assistant to Moritz Litten (1899–1902) and for Ernst Viktor von Leyden (1902–1906).

[1] From 1900 to 1904, Michaelis continued his study of clinical medicine at a municipal hospital in Berlin, where he found time to establish a chemical laboratory.

In 1905 he accepted a position as director of the bacteriology lab in the Klinikum Am Urban, becoming Professor extraordinary at Berlin University in 1908.

An equation of the same form and with the same meaning appeared in the doctoral thesis of Victor Henri, a decade before Michaelis and Menten.

[10][11] However, Henri did not take it further: in particular he did not discuss the advantages of considering initial rates rather than time courses.

In his later career he worked extensively on quinones, and discovered Janus green as a supravital stain for mitochondria and the Michaelis–Gutmann body in urinary tract infections (1902).

He found that thioglycolic acid could dissolve keratin, a discovery that would come to have several implications in the cosmetic industry, including the permanent wave ("perm").

Perhaps more honest than tactful, Michaelis advised him to take up teaching, and thus catalysed the invention of the Suzuki method.

[18] Michaelis was married to Hedwig Philipsthal; they had two daughters, Ilse Wolman and Eva M. Jacoby.