The world’s first “immortal” human cells, the HeLa cell line, was started by researcher George Otto Gey (and his lab assistant Mary Kubicek) back in 1951 at Johns Hopkins.
They took a tiny sample of cervical cancer cells from Henrietta Lacks, isolated cells from it (essentially starting from one or a few specific cells), put them in a culture dish/flask with nutrient-rich medium (no body needed), and — unlike every previous human cell attempt — they just kept dividing and staying alive indefinitely.
Those cells (and all their descendants) have now been thriving on nutrients alone for over 74 years and are still used in labs worldwide today.
Here’s a clear, straightforward link to the story:
https://en.wikipedia.org/wiki/Henrietta_Lacks (the HeLa page has all the details on Gey’s work and how it started).
A shorter, easy-read version from the BBC:
https://www.bbc.co.uk/bitesize/articles/zv6cydm