Tequila Sunrise

A cocktail made from tequila and orange juice with grenadine. The grenadine, being more dense, settles to the bottom of the glass creating gradations of colour from red at the bottom to orange at the top, hence the 'sunrise' in the name. Penny makes a tequila sunrise for Leonard while practising her bartending skills. He begins to expound about the way liquids with different specific gravities interact within a cylindrical container, but catches himself and just says thank you.