TRIzoL is a reagent used to isolate high quality RNA from cells and tissues by maintaining RNA integrity during tissue homogenization while disrupting cells. The homogenized samples are separated into aqueous and organic phases through centrifugation with chloroform. RNA remains solely in the aqueous phase, while DNA and proteins are recovered from the other phases. The isolated RNA is then precipitated from the aqueous phase using isopropyl alcohol, washed with ethanol, and dissolved in water. This pure RNA can be used in downstream applications like Northern blot analysis and molecular cloning. The procedure involves homogenizing cells in TRIzol, separating the homogenized solution into phases, and precipitating and purifying the RNA.