Okay, so imagine you're a little kid in a really long time ago place called the Middle Ages. It's a time when there aren't many machines and things, and people have to do everything by hand. This time lasted from about the 5th century to the 15th century.
Now, even though things were a little more difficult, people in the Middle Ages were still really interested in learning new things, especially about science. They wanted to know how the world worked and how they could use that knowledge to make things better.
One really famous scientist from that time was named Alhazen. He was from Iraq and lived from 965 to 1039. Alhazen studied optics, which is how light travels and how our eyes see things. He used experiments to figure out how our eyes work and wrote a famous book called "The Book of Optics" which is still used by scientists today.
Another scientist, a lady named Hildegard of Bingen, lived in Germany from 1098 to 1179. She was known for her great knowledge of medicine and plants. She was a really smart lady and even wrote several books on medicine.
There were also some famous mathematicians in the Middle Ages. One was Leonardo Fibonacci, who wrote a really important book about numbers and showed people how to use them in new ways. Another was an Arabic mathematician named Al-Khwarizmi, who is famous for inventing algebra, which is like solving puzzles with numbers.
So in summary, even though the Middle Ages were a long time ago and people didn't have fancy machines like we do now, they were still really smart and curious about the world around them. They studied science, math, and medicine, and some of their ideas are still used today!