Studies have shown that in the last two decades, the size of supermarkets has increased by a third.

At the same time, the population of city centers - such as Center City Philadelphia - are rising.

Food-shopping options closer to home usually mean a trip to a small corner store or to a large specialty retailer such as Trader Joe's or Whole Foods.

Supermarket operators typically avoid downtowns because of the rents. Philly also does not have too many vast spaces that would lend themselves to large stores.

How about a middle ground?

You may have noticed the sign advertising a new store called Everything Fresh at 1222 Walnut St., the newly rehabbed property known as the Stapler Building. The sign said the product line will include organics and prepared foods.

But let's get behind the sign.

I can tell you that Everything Fresh has some serious firepower behind it.

It's backed by Ahold USA - the domestic side of the Dutch food conglomerate Royal Ahold NV that owns such brands as Giant Food and Martin's Food Markets.

An Ahold USA spokeswoman told me that the company has set up a team to look at what the company calls "new formats."

Everything Fresh - "opening soon," in the words of its rep - will be part of this project to test ideas.

Where the median U.S. supermarket occupies about 46,000 square feet, Everything Fresh will have selling space of 3,700 square feet on the building's ground floor (plus 1,500 feet in the basement for prep). It's just a touch smaller than the Di Bruno's store at Ninth and Sansom Streets (4,500 square feet).

The spokeswoman cautions that this will be a test store and "may not be representative of a new format, which is expected to be deployed in the future."

Corporate speak for: If it works, we'll do more. If it doesn't, we tried.