A prokaryote is a simple type of cell that lacks a nucleus and other membrane-bound organelles. These organisms are usually single-celled and are classified into two main groups: bacteria and archaea. Prokaryotes are incredibly diverse and can be found in various environments, from soil to extreme conditions like hot springs. Despite their simplicity, prokaryotes play essential roles in ecosystems. They help decompose organic matter, fix nitrogen in the soil, and even contribute to human health through the gut microbiome. Their ability to reproduce quickly allows them to adapt rapidly to changing environments, making them vital for life on Earth.