What we think of as 'science' today didn't really exist in Isaac Newton's lifetime. He would have described himself as a 'natural philosopher', although we recognise him as one of the most important scientists of all time.
Newton was born on Christmas day, three months after his father had died. His mother remarried when he was three years old and left him to be brought up by his grandmother. Newton disliked his stepfather and resented his mother so much for marrying him that he threatened to burn down their house down with them in it. Fortunately, he didn't carry out his threat. Our understanding of the world would have progressed much less quickly if he'd been hanged!
Isaac Newton's scientific theories stemmed from a fascination he developed with mathematics even though maths wasn't taught at the school he went to. When he was seventeen, his mother decided he should leave school and become a farmer, which he hated. When the headmaster at the school persuaded Newton's mother to let Newton return to school, he won a place at the University of Cambridge, although he had to pay for it by working as a valet while he was studying.
Sir Isaac Newton, painted by the go-to-painter of the Restoration period, Sir Godfrey Kneller.
At Cambridge, Newton studied the teachings of Aristotle, and read the more modern ideas (modern at that time!) of Galileo and Descartes. Although he wasn't a star student, he continued his studies at home after he graduated. Over the next two years, he developed a theory that later became calculus (the mathematical study of change), and studied optics (the behaviour of light) and the laws of gravity.
The story of him discovering gravity when an apple fell on his head isn't quite true, even if we'd like to think that being hit over the head can give you a lightbulb moment. But Newton did see an apple fall from a tree in his orchard one day. Rather than wondering whether it was ripe enough to eat, or worrying that the fruit had got bruised when it hit the ground, he suddenly wondered why it fell downwards rather than up or sideways. Thus was born one of the key theories that explain to us how the world works. It's just as well it was him in that orchard, not me. If it was down to me to make scientific discoveries, we'd all still believe that the earth was flat and spend our days wondering what was for dinner.