Excretion is different in multi-cellular organisms as compared to unicellular organisms. How?

In unicellular organisms, excretion is performed by a single cell by the process of diffusion through the body surface. Whereas, in multi-cellular organisms, different life processes are performed by different cells and organ-systems (nervous system, excretory system, circulatory system, etc). Multi-cellular organisms use specialised organs such as lungs, kidneys, nephrons, skin, malphigian tubules, etc to eliminate waste products from their body.