1590: Invention of the microscope Janssen (as Attributed to Galileo in 1609).1665: Discovery of the cell by Robert Hooke.

1866: Publication of Mendel's laws on inheritance .

1866: Identification of "mongolism" by John Langdon Down, now called trisomy 21 or Down syndrome.

1880: first observation of chromosomes by Flemming.

1911: Theory of heredity demonstrated by Thomas Hunt Morgan.

1944: Identification of the chemical nature of DNA by Oswald Avery, Colin MacLeod, and McCarty.

1950: Observation of the helical shape (corkscrew) DNA by Rosalind Franklin and Maurice Wilkins.

1950: Discovery of bases constituting the DNA by Erwin Chargaff.

1952: Detection of DNA as the molecular carrier of genetic information by Alfred Hershey and Martha Chase.

1953: Determination of the structure of the DNA molecule by James Watson and Francis Crick.

1956: Determination that the number of chromosomes in humans is 46 (23 from the father and 23 from the mother) by JH Tijo and A. Levan.

1956: First use of amniocentesis in the diagnosis of genetic disease by Fuchs and Riis.

1957: Discovery of the reproductive mechanism of DNA (replication), by Matthew Meselson and Franklin Stahl.

1959: Publication of the discovery of trisomy 21 by Jerome Lejeune, Marthe Gautier, Raymond Turpin.

2003: End of the sequencing of the human genome (Human Genome Project) launched in 1993 involving 18 countries.

2012: First major pharmaceutical company begins a Phase I clinical trial on a drug to improve cognition in Down syndrome

2012: Jérôme Lejeune Institute begins clinical trial on the use of folinic acid and thyroxine to improve psychomotor development of young children with Down syndrome.