what are cells

Cells are the basic structural and functional units of all living organisms. Each cell is a microscopic unit enclosed by a membrane, containing cytoplasm and often specialized structures called organelles, which carry out specific functions necessary for life. Cells can be broadly categorized into two types: eukaryotic cells, which have a nucleus and membrane-bound organelles, and prokaryotic cells, which lack a nucleus but have a nucleoid region. Cells are capable of replication, protein synthesis, and motility, and they form the foundation of tissues, organs, and entire organisms, from single-celled bacteria to complex multicellular beings like humans.