I gotta say mRNA vaccines. It's not technically a 21st century invention, but much of the work to make them viable started in the early 2000s. The speed at which the COVID vaccine got developed and widely deployed was honestly incredible and a massive W for humanity. I remember thinking a vaccine would be years away.
Vaccines in general.
Then we're very far away from the 21st century though.
I gotta say mRNA vaccines. It's not technically a 21st century invention, but much of the work to make them viable started in the early 2000s. The speed at which the COVID vaccine got developed and widely deployed was honestly incredible and a massive W for humanity. I remember thinking a vaccine would be years away.
Vaccines in general.
Then we're very far away from the 21st century though.