Can reducers and mappers be on the same data node?

I have started reading about Big Data and Hadoop, so this question may sound very stupid to you.

This is what I know.

Each mapper processes a small amount of data and produces an intermediate output. After this, we have the step of shuffle and sort.

Now, Shuffle = Moving intermediate output over to respective Reducers each dealing with a particular key/keys.

So, can one Data Node have the Mapper and Reducer code running in them or we have different DNs for each?