Hello Dewi Murda

Yes. Formazan crystals form in living cells due to a process called reduction of tetrazolium salts by mitochondrial enzymes. Viable cells, especially those with active mitochondria, possess enzymes called dehydrogenases that can reduce tetrazolium salts. Specifically, MTT is taken up by viable cells and converted into a purple, water-insoluble formazan product within the mitochondria. The reduction of the tetrazolium salt by these enzymes produces formazan, a colored product that is typically insoluble in water and tends to form crystals. While formazan forms crystals within the cells, it can be solubilized using a solvent like DMSO.

The intensity of the formazan color is directly proportional to the number of viable cells, making it a useful indicator of cell viability and metabolic activity.

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Malcolm Nobre thank you very much for your the best answer

You're welcome.