Prokaryotes are simple, single-celled organisms that lack a nucleus and other membrane-bound organelles. They are among the oldest forms of life on Earth and can be found in various environments, from soil to extreme conditions like hot springs. The two main types of prokaryotes are bacteria and archaea, each with unique characteristics and functions. These tiny organisms play crucial roles in ecosystems, such as decomposing organic matter and cycling nutrients. Some prokaryotes are beneficial to humans, like those used in fermentation for making yogurt, while others can cause diseases. Understanding prokaryotes helps scientists explore the diversity of life and its impact on our planet.