People know Albert Einstein as someone who created a revolution in Physics with his pioneering theories. However, there are a lot of things that most people don't know about the great physicist. The following are 30 things that we didn't know about him.

1. At the very young age of 16, he relinquished his citizenship of Germany. In fact, he'd rather be a world citizen than a nationalist. For some time he remained stateless until he accepted the citizenship of Switzerland in 1901.

2. There was only one female student in his class named Mileva Maric at the Zürich Polytechnic where he studied. Maric had considerable interest in science and maths. She aspired to be a physicist but once married she gave up her ambitions.

3. Interestingly, the FBI maintained a dossier on Einstein running into a whopping 1427 pages that contained information on his connection with socialist and pacifist organizations. In fact, Hoover wanted him deported according to the Alien Exclusion Act, but the American State Department overruled this.

4. Einstein had a baby born out of wedlock in 1902, when Mileva was in Serbia, living with her family. The child was christened Lieserl who was either given away for adoption or died while still a baby. He never saw his daughter.

5. Einstein divorced his first wife, and for her to agree to the divorce he offered her the money he got from the Nobel Prize which came to $32,250, a considerable sum in those days time.

6. Einstein went on to marry his first cousin Elsa who was a daughter of the sister of his mother.4

7. Einstein was an avid supporter of free speech and civil rights. This made FBI maintain a dossier about him and wanted him out of the country.

8. Many persons used to enter Einstein's house, stand in the patio, come down and get their photographs taken as if they were coming out of his house after meeting him. He used to let them do it if it gave them any pleasure.

9.  Einstein's son was suffering from schizophrenia and so was institutionalized for almost all of his grown-up life. After immigrating to America in 1933, he didn't see his son again.

10. Fritz Haber the German scientist who was the father of chemical warfare was a close friend Einstein while in Germany. Haber developed a lethal form of chlorine gas that could spread through the trenches and kill soldiers by suffocating them.

11. Einstein had a romantic relationship with Margarita Konenkova, an alleged spy from Russia in 1935. However, this wasn't confirmed by any historian.

12. While at college in Switzerland he became interested in sailing. He used to sail a boat in a lake, to relax. Ironically, he could not swim but continued with his hobby all through his life.

13. It was Einstein's wish that his body should be cremated and the ashes scattered. However, before this could be done a pathologist named Thomas Harvey of the Princeton Hospital did an autopsy on the great scientist's body, and took out his brain. Harvey did this to unravel the secret of Einstein's genius at first, and then sent parts of the brain to various researchers. Since he did it without permission, he lost his job at the hospital. Eventually, the brain was returned to Princeton Hospital, in 1998.

14. Einstein was invited to become the President of Israel when the then president Chaim Weizmann died in 1952. However, he declined this saying that he had no natural aptitude to deal with people as also he was becoming old.

15. Einstein always had a disheveled look. Apart from this, he never wore socks. He considered socks troublesome as they tend to develop holes. He also thought that one of them is just fine, so why wear two.

16. His father showed Einstein a pocket compass that had a mesmerizing effect on him. He wondered what made the needlepoint at just one direction. This event is said to be the reason for his attraction to science.

17. Einstein even invented the refrigerator that worked on alcohol gas. Although it was duly patented in 1926, new technology rendered it useless. He invented this when he heard that the refrigerator that emitted sulfur dioxide poisoned a family.

18. Einstein was a compulsive smoker. On his way to his office at Princeton University, he was seen trailing smoke in his wake. His baggy clothes, unkempt hair, and his briar pipe was part of the Einsteinian image. He even believed that smoking a pipe imparted objective judgment in the affairs of men, although he never refused a cigarette when offered.

19. Einstein was born with a head that had a weird shape with the back of the head bigger than usual. However, after a few weeks, his head took on a normal shape.

20. Einstein had difficulty speaking and was unable to speak until he was four years old.

21. Interestingly, Einstein wrote his initial scientific paper when he was only sixteen years old. It was titled "The Investigation of the State of Aether in Magnetic Fields."

22. In 1902, Einstein's father's business was closed down and went into bankruptcy. The ensuing perilous financial condition made their life very hard. Forced to earn a living, he began giving tuitions to children.

23. While studying at the Polytechnic in Switzerland, Einstein read about the Scottish Physicist James Maxwell's electromagnetic theories. While doing so, he came to the surprising conclusion that the speed of light remained constant, something that Maxwell was unaware of. It was this fact that led to the development of his relativity principle.

24. 1905, was Einstein's Miracle Year when he submitted his doctoral thesis and four of his groundbreaking papers were published by the prestigious physics journal Annalen der Physik. These papers changed the whole system of modern physics.

25. One of his papers "Equivalence of Matter and Energy," portrayed Einstein's renowned formula E=mc2.

26. Einstein's papers created a controversy among the whole academic world, and they were ignored. However, Max Planck who established the quantum theory confirmed his work after conducting experiments. This made Einstein a prominent figure in physics.

27. After becoming popular, Einstein began to travel frequently, incurring a lot of expense, which he could ill afford and it caused a lot of trouble in the family.

28. In 1930, Einstein met the famous scientist Edward Hubble. At this meeting, he told Hubble that his cosmologic constant that dealt with the inert shape and size of the universe was his "The Greatest Blunder." However, this 'blunder' became the whole basis in the study of the dark energy prevailing in the universe.

29. Dr. Thomas Sowell used the medical term 'Einstein Syndrome' to explain delayed speech in people who are remarkably intelligent. This is because Einstein was unable to speak until he became 4 years old.

30. Einstein's eyeballs were placed in a safe box and preserved in the city of New York.