No one knows who invented pencils or when it happened. A Swiss described a pencil in a book in 1565. He said it was a piece of wood with lead (Pb) inside it. (Lead is a very heavy metal). Pencils werent popular, and people continued to write with pens. They used bird feather as pens. Then in 1795, someone started making pencils from graphite and they became very popular. Graphite is a kind of coal. (Coal is black, and we burn it for heat and energy). Today, people make pencils in the same way. They grind the graphite, make it into the shape of a stick, and bake it. Then they put it inside a piece of wood. One pencil can write 50,000 English words or make a line 55 kilometers long. People wrote with feather pens and then used pens with metal points. They had to dip the point into ink after every few letters. Next someone invented a fountain pen that could hold ink inside it. A fountain pen can write several pages before you have to fill it again. Two Hungarian brothers, Ladislao and Georg Biro, invented the ballpoint pen that we all use today. They left Hungary and started making ballpoint pens in England in 1943 during World War II. English pilots liked them. They couldnt write with fountain pens in airplanes because ink leaked out. Later, a French company called Bic bought the Biros company. Someone calls ballpoint pen a bic. The Australian call them biros. Whatever we call them, we use them every day. làm được câu nào thì làm