Do you know about the scientific discovery that motivates India's National Science Day, celebrated today. India celebrates the #NationalScienceDay🇮🇳 in commemoration of the discovery of the Raman Effect. If you do not know about this phenomena, here is a simple explanation. Imagine you are in a dark room, shining a torch at a glass of water. While most of the light passes straight through the glass with a bit of scattwer, some light bounces back with the same colour it went in to the fluid (water in this case). But a tiny bit of light comes back (or is scattered) at a different colour (or wavelength). That is the Raman Effect! The important point is that the change in colour or wavelength of the original light due to Raman scattering holds clues to the fluid or substance that scattered it. Therefore Raman effect is a powerful scientific tool to explore the properties of different constituents of the fluid, that is molecules. Why does this happen? When light hits a molecule, it gives that molecule a little nudge. Most photons (light particles) bounce off without any change in energy (which determines its wavelength or colour). But a few photons exchange energy with the molecule. They come out slightly different, shifted in energy (colour or wavelength). This interaction carries the fingerprint of exactly what that molecule is made of. And boom you have discovered a powerful scientific tool of exploration. That's what Prof. C.V. Raman achieved in Kolkata on 28 February 1928.