How to make a quick and healthy lunch

Lunch! We have to eat it. But it can be hard to make a lunch that is quick and healthy. It may feel easier just to go buy something from a restaurant or fast food place. I really don't have a lot of time for lunch. I may be able to walk away from my desk for about 20 minutes during the week. Sometimes, I eat and work at the same time. I know this is not a very healthy behavior.