Lots of people that time were dying because of a disease called Smallpox
Edward Jenner was curious why this happened
one day, he saw a milkmaid milking a cow and she had cowpox on her. edward jenner realised she didnt have smallpox so he started investigating..
so he found a young boy that didnt have smallpox or cowpox yet and asked him wether he could investigate.
Edward took fluid from a cowpox blister and scratched it into the skin of the boy A single blister rose up on the spot, but James soon recovered.he ended up not having smallpox and he lived until a ripe old age