After a food tour of Chicago with Evelyn Thompson, it's impossible to look at an ethnic grocery in quite the same way.

That's because Thompson, an avid cook, former teacher and longtime Chicagoan, has been hosting private tours of the city's grocers since 1994, when she got her start by presenting a talk on them to the Culinary Historians of Chicago. Not only does she know the use and history of each spiny vegetable; she also knows the stores' owners.

Thompson's Ethnic Grocery Tours, usually conducted in her maroon Corolla station wagon, are custom-made depending on clients' interests. Though we traveled by car, we decided to cover the different ethnicities represented by several stops on the Chicago Transit Authority (CTA) Red Line elevated train in the North Side, starting at Howard Street and proceeding down Clark Street, through the neighborhoods of Rogers Park, Andersonville and Uptown.

We started at Rogers Park Fruit Market (7401 N. Clark St., 773-262-3663), in a former gas station. Thompson pointed out the nopalito, prickly pear cactus pads that -- when despined, cubed and shrink-wrapped -- make excellent salads and are often added in soups; the herb bundle epazote, which smells like kerosene but is good for soups and killing intestinal worms; and watercress, valued by Asians as a blood purifier.

Across the street at the Supermercado Morelia (7334 N. Clark St., 773-761-3291), a Mexican grocery, we salivated over an assortment of more than 20 types of pan dulce (pastries). Thompson bought a wedge of cheesecake to demonstrate its difference from the American version -- the filling was thick and pudding-like. I also had a satisfying besito, whose name means "kiss" and describes how its two circles of white cake are melded together by red jelly and coconut.

We ventured to Devon Avenue -- possibly the most interesting international street in Chicago, with a mix of Assyrians, Pakistanis, Indians, Turks, Arabs, Greeks, Russians, Poles, Orthodox Jews, Mexicans, Cubans and Eastern Europeans -- to the Cuban grocery La Unica (1515 W. Devon Ave., 773-274-7788). We ordered at the counter in back (entrees start at $4.99) and ate at one of the 10 tables. The menu: strong espresso-size cups of thick Cuban coffee, fried yellow plantains and yuca con mojo (boiled and vinaigretted yuca, a potato-like vegetable also known as cassava and manioc). The Spanish yuca con mojo, as the potato-salad-like dish is known, was tangy and terrific, with fresh salsa verde.

Down the street at BM Bakery (1443 W. Devon Ave., 773-381-1321), the smell of fresh-baked Bosnian bread filled the air. A group of men conversed in their native tongue in the bright open space while eating plates of savory boiled meat and bread, cigarette haze hovering over their table. Other specialties include cheese breads and kifla, puffy, yeasty breads that look like pita but which Thompson said are good substitutes for hamburger buns. At 60 cents apiece, the price was right.

Back in the car, we drove south a couple miles to Andersonville, an area more gentrified than the neighborhoods farther north. Although it was settled by Swedes, a community of Assyrians who landed there in the early part of the 20th century created today's Middle Eastern community, which includes several busy restaurants.

The Middle East Bakery & Grocery (1512 W. Foster Ave., 773-561-2224) has -- along with a wide range of staples used for Middle Eastern cooking, including tahini and long-handled copper Turkish coffee pots -- a case containing freshly prepared foods ranging from pickled turnips and brochette to multiple varieties of hummus. You can also buy olives by the pound ($2.95), sandwiches and flat breads. The bread, often hot from the oven, includes a flavorful new low-carb option: a crunchy seven-grain pita, containing wheat, barley, potato rice flour, soy, grits, bulgur wheat and rye meal. From there we headed to Broadway and Argyle Avenue, with its thriving district of Vietnamese (and, to a lesser extent, Chinese) restaurants, cafes, butcher shops and stores. At Bale French Bakery (5018 N. Broadway, 773-561-4424), you can buy banh mi, the wonderful sandwiches made from a baguette and a spread of fresh mayonnaise, cilantro, pickled slivered carrots and fresh cold cuts, such as barbecued pork. The bakery also offers prepackaged cold entrees, such as sliced pate with bean sprouts, other vegetables and a tangy sauce, and sweets such as sesame balls filled with red bean paste and glasses containing distinct levels of tapioca, black-eyed peas and coconut cream.

Thompson's tour ended a few doors south at the Thai Grocery (5014 N. Broadway, 773-561-5345), where we looked at the produce, including green mangos and green papayas. The counter service area in back serves up pad thai by the pound ($3.95 a quart) and mild Thai sausage ($5 for a package of five).

From the Thai Grocery, it was an easy walk through the busy foot traffic of Argyle, past butcher and seafood shops where brown and crispy roasted fowl hang on strings just inside front windows, to the El station. After my afternoon of grazing from grocery to grocery, I needed the exercise.

-- Catherine Arnold

Up to four people can take one of Evelyn Thompson's tailor-made grocery tours at one time. Cost for the 31/2- to four-hour tour: $60 for one, $70 for two, $85 for three and $110 for four. Details: 773-465-8064, Ext. 2 ,

Evelyn Thompson's ethnic food tours in Chicago stop for samples at such local markets as the Middle East Bakery & Grocery.