The cell is the basic structural and functional unit of life. Human cells contain organelles such as nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes, each performing specific functions.
A tissue is a group of similar cells performing a common function. The four basic tissues are:
Epithelial tissue covers body surfaces, lines cavities, and forms glands. It functions in protection, absorption, secretion, and filtration.
Connective tissue supports, binds, and protects organs. Examples include bone, cartilage, blood, and adipose tissue.