Which breakfast cereal is made by being heated to high temperatures and cooled immediately?

The breakfast cereal that is made by being heated to high temperatures and cooled immediately is Puffed Rice or Puffed Wheat.

This process is called extrusion. Here's how it works:

1. Heating: Grains (like rice or wheat) are heated to a very high temperature, causing the starch inside to gelatinize (turn into a gel).

2. Expansion: The pressure inside the grain increases as the starch gelatinizes.

3. Cooling: The heated grains are forced through a die, which causes them to rapidly expand and cool. This results in the puffed, airy texture that we know and love.