Quantum physics describes the behavior of matter and energy at the smallest scales. Unlike classical physics, quantum mechanics reveals that particles can exist in multiple states simultaneously through a phenomenon called superposition. The uncertainty principle, formulated by Werner Heisenberg, states that certain pairs of physical properties cannot be simultaneously measured with arbitrary precision. Quantum entanglement allows particles to be correlated in ways that transcend classical physics, enabling instantaneous information sharing across vast distances. Applications of quantum physics include lasers, transistors, MRI machines, and emerging quantum computers. The field continues to challenge our intuitions about the nature of reality and causality.