Organ development refers to the process by which organs form and mature in living organisms. This process begins during embryonic development, where cells differentiate and organize into specific structures. Each organ has a unique timeline and sequence of development, influenced by genetic and environmental factors. During organ development, various signaling pathways and genes play crucial roles in guiding the formation of tissues and organs. For example, the heart develops from a simple tube into a complex structure with chambers, while the lungs form from branching structures that increase surface area for gas exchange. Proper organ development is essential for overall health and function.