Why do hot things burn us?

An object is said to be hot if its temperature is more than our body temperature. If we touch such an object, heat flows from it to our body and we feel its sensation. Similarly, an object is said to be cold if its temperature is lower than our body temperature.
When we touch it, heat flows from our body into that object. Do you know why it happens like that?
We know that our body is made up of cells. And consequently these cells are made up of molecules. At normal body temperature these molecules are in motion. When a hot substance touches some part of our body, the fast moving molecules of that substance accelerate the motion of the molecules of the cells in the affected part. And when the molecules of cells stand the fast vibrations the cells start breaking up. It is the breaking up of the cells that gives the burning sensation. To repair the damaged cells, the blood circulation becomes faster in the affected area. That is why the affected part becomes red.
When the temperature of the object touching the body is very high, a large number of cells and nerves break up. The heat of the substance dehydrates cells of the skin and they break up. This is called burning.
Sometimes very hot substances destroy the fat, molecules and bones. This causes deeper wounds in the body. The scars caused by such burning are removed by grafting the skin from some other parts of the body.