This document covers the topic of movement into and out of cells for CAIE IGCSE Biology. It explains the three key processes: diffusion, osmosis, and active transport. Diffusion is defined as the net movement of particles from high to low concentration, driven by kinetic energy, and influenced by factors such as concentration gradient, temperature, surface area to volume ratio, and distance. Osmosis is described as the net movement of water molecules across a partially permeable membrane, with detailed examples of how it affects plant cells (turgid, flaccid, plasmolysis) and animal cells (lysis or isotonic conditions). Active transport is presented as the movement of particles against a concentration gradient using ATP and carrier proteins, with examples like ion uptake in root hair cells. The guide also introduces endocytosis (phagocytosis), where white blood cells engulf pathogens. A comparison table highlights the differences between diffusion, osmosis, and active transport in terms of energy use, direction, substances moved, and membrane requirements. With clear definitions, diagrams, and practical examples such as the dialysis tubing experiment, this resource helps students understand and master essential transport processes in cells.