21. Constantine the Great

Flavius Valerius Aurelius Constantinus commonly known as Constantine I, Constantine the Great, or Saint Constantine, was born on 27 February 272. His father name was Constantius Chlorus and mother name was Helena. He was Roman Emperor from 306 to 337.
                     He was the first Christian Roman emperor. He reversed the persecutions of his predecessor, Diocletian, and issued the Edict of Milan in 313, which proclaimed religious tolerance of Christians throughout the empire.
                     The foremost general of his time, Constantine defeated the emperors Maxentius and Licinius during civil wars. He also fought successfully against the Franks, Alamanni, Visigoths, and Sarmatians during his reign.
                      He even resettled parts of Dacia which had been abandoned during the previous century. Constantine also transformed the ancient Greek colony of Byzantium into a new imperial residence, Constantinople, which would be the capital of the Eastern Roman Empire for over one thousand years. He died on 22 May 337 (aged 65) in Nicomedia (modern-day Izmit, Turkey).

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20. Antoine Laurent Lavoisier

                      Antoine Laurent de Lavoisier (also Antoine Lavoisier) was born on 26 August, 1743 in Paris France. He is known as "The Father of Modern Chemistry". He was a French nobleman prominent in the histories of chemistry and biology. He stated the first version of the law of conservation of mass, recognized and named oxygen (1778) and hydrogen (1783), abolished the phlogiston theory, helped construct the metric system .
                  He wrote the first extensive list of elements, and helped to reform chemical nomenclature. He discovered that, although matter may change its form or shape, its mass always remains the same.
                  He was an investor and administrator of the "Ferme Generale" a private tax collection company; chairman of the board of the Discount Bank (later the Banque de France); and a powerful member of a number of other aristocratic administrative councils.
                 All of these political and economic activities enabled him to fund his scientific research. At the height of the French Revolution, he was accused by Jean-Paul Marat of selling watered-down tobacco, and of other crimes. He was guillotined on 8 May, 1794. 
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Antoine Laurent Lavoisier