The Impossible Burger has become a household name (and a South Park episode), but in 2016, it had a modest cult following of vegetarians who paid upwards of $10 a patty at high-end restaurants. Meat eaters and fast-foodies were among the least expected markets for the pricey Impossible, but after a successful pilot program, it landed on the menu of every White Castle in America…for $1.99.

Today, the Impossible Burger is available in more than 30,000 restaurants in America — as well as Australia, Canada, Hong Kong, Singapore and more. This success story exemplifies why it’s crucial to look for new revenue streams for your products or services by examining them from fresh angles. As CEO of an accelerated learning company, one of my favorite techniques for achieving this goal is called Where/When/How/Who Else?

By simply identifying situations in which your product or service isn’t currently being used, you can discover opportunities to innovate and drive growth. After leading companies like Google and Novartis through this exercise, I recommend conducting it in teams of 3 to 4 people and then regrouping for a larger discussion after small teams have brainstormed ideas in all four categories.

To illustrate, let’s imagine you’re a transportation agency looking to monetize your fleet of school buses. Direct your first line of thinking to where else consumers might interact with school buses. This could translate into usage in other cities or countries, as well as local spaces, sites or scenarios. More examples of “Where Else” for school buses could include indoors; on water; or at farmers markets.

Now, let’s explore the “When Else” category. As in, when else could people utilize school buses? Think about alternative times, such as evenings; or unexpected occasions, such as holidays and lunch hours; or different days, such as when schools aren’t using them. In this case, school buses could be alternatively used on weekends, after-hours, summer months, snow days or after the school district retires them.

Next, think about how else could you utilize the fleet of school buses? “How else” refers to alternative uses and contexts, so consider the opposite of its current educational use, or how you might bundle it with something else. Moreover, could it be utilized in an extreme scenario? An opposite use for a school bus could be a party bus. An alternative context might be a food truck; airport shuttle; or a mobile art gallery. An extreme use could be a skatepark hurdle or a prop on a paintball course.

And finally, who else besides your existing consumer base could benefit from the fleet of school buses? “Who else” refers to different age groups, lifestyles and audiences that your product or service is not currently reaching. So, start by listing the age groups and lifestyles of audiences who don’t use it. Examples could be children of car owners; adults without children; tourists; etc.

At this stage of the exercise, you should have dozens of ideas in four different categories. As a group, share these and identify the most strategic and promising ideas before voting on the top two. Then, flesh out each concept by thinking about how could you create an experience around this idea? Do you have the internal capabilities to develop it? And do any of the ideas have partnership or sponsorship potential?

Moreover, could you combine your top two ideas with ancillary ideas to further build out the concept? For example, could the school buses be repurposed in summer as a Museum of Modern Art pop-up shop that’s parked in a touristy area? In that single expanded concept, four “Elses” have been incorporated: “parked buses,” “summer,” “mobile art gallery” and “tourist.”

From upscale vegan burgers at fast food joints to MOMA-wrapped school buses, this technique sets the stage for innovative thinking. It also enables you to tap existing products and services for new audiences, markets and revenue streams. Whether you’re an established brand or a start-up, identifying new market opportunities on a regular basis is key to driving growth.