NECESSITY IS THE mother of reinvention, too.

While the economic downturn has many business owners cutting back and curbing investments, a handful of companies are actually expanding into new markets or taking their business in an entirely new direction in order to stay afloat. Some businesses, like RTI Laboratories in Lavonia, Mich., are turning overcapacity into rental income, while others are providing services they've never offered before – and at cheaper rates and faster turnaround times than the competition.

“If you realize that your business is suffering, rather than wait for the economy to turn around, take this opportunity to reexamine your business,” says Donald F. Kuratko, executive director of the Johnson Center for Entrepreneurship and Innovation at Indiana University's Kelley School of Business. Look for opportunities in your market or new markets, then consider how your company might meet them, he says.

Here are four businesses that are doing just that.

Meet the 4 business owners here >>>