It is your sense of smell that quickly tells you there is good food in the kitchen, or your smelly socks need to be washed.          But how do we recognize smell? Particular smells turn on certain groups of brain cells , scientists say. When your nose catches a slight smell of something, one of 1,000 different types of odor-receiving  cells pick it up. These cells send an electrical signal to a special part of the brain.          A group of scientists studied mouse brains using some particular odors like vanilla, apples and fish. They looked at thin slices of each mouse's brain to see which brain cells had been turned on by each odor. The scientists discovered that each odor produces a similar pattern of active cells in different mice. So, a certain combination  of cells can tell a mouse that it is smelling vanilla, apples, fish, or any one of the thousands of other smells.          Scientists could use studies like this to create a map. It could show which parts of the brain are activated  by different smells. Some other scientists, however, say that researchers should also study animals that do not live in a lab, which have spent their lives smelling things in the natural world. With more smelling experience, they might show quite different patterns. By doing mouse experiments, the scientists   _  .
found different types of odor-receiving cells in mice found each smell creates a similar pattern of active cells in different mice showed that different mice have different brain cells proved that a certain cell can tell a mouse what it smells