Specifically, she proposed the endosymbiotic theory, which states that:
* Mitochondria originated from aerobic bacteria that were engulfed by larger prokaryotic cells.
* Chloroplasts originated from photosynthetic bacteria that were engulfed by larger prokaryotic cells.
This theory suggests that these engulfed prokaryotic cells did not get digested by the host cell but rather lived within them and eventually formed a symbiotic relationship, evolving into the organelles we know today.
Margulis' theory has been widely accepted and supported by a vast amount of evidence, revolutionizing our understanding of the evolution of eukaryotic cells.
