**2. Introduction to taxis**

Molecules are always in motion irrespective of their state. Molecules in solid state have least freedom while in gaseous state have maximum freedom. Freedom of movement of molecules in liquid phase lies between molecules in solid and gaseous phases. Heat and temperature are factors that affect the movement of molecules. Enhance temperature increases the translational movement of molecules. Movement of molecules can be random or directed towards certain stimuli. Random movement is termed as "kinesis" while directed movement towards certain stimuli is termed is "taxis". For taxis, there is sensory component to detect the attractant and motor component to enable the movement towards the stimuli [2]. Taxis are classified on the basis of the stimulus into various categories.
