These organisms were prokaryotes, meaning they lacked a nucleus and other membrane-bound organelles. They likely arose from abiotic (non-living) materials through a process called abiogenesis.

While the exact nature of these first organisms is still debated, scientists believe they were likely thermophiles (heat-loving) and anaerobes (living without oxygen) as the early Earth's atmosphere was devoid of oxygen.

They obtained energy through chemosynthesis, using inorganic compounds like hydrogen sulfide or iron for energy production.

These early prokaryotes eventually evolved into cyanobacteria, which were the first organisms to photosynthesize and release oxygen into the atmosphere. This event had a profound impact on the evolution of life on Earth.

While we don't have fossils of the very first organisms, scientists study fossils of early bacteria and other microorganisms, as well as genetic evidence to piece together the story of life's origins.