As the blood passes through the capillaries some amount of it oozes out in the surrounding tissues. This is known as tissue fluid or interstitial fluid. When this fluid enters the lymphatic system it is known as lymph. Lymph is a colorless fluid as it lacks haemoglobin. It contains cells known as Lymphocytes which is important for immune system. The Lymphatic system consists of lymphatic capillaries, nodes, vessels and ducts. The lymphatic capillaries join to form lymphatic vessels. Large lymphatic vessels finally pour into one of the two principal vessels: Thoracic duct or Right Lymphatic duct. The thoracic duct receives lymph from the entire left side of the body.