Fathers are in an excellent position to explain the whole world of things and ideas to their kids -- what better place to begin than by explaining themselves?

Taking your kids with you to the place where you work is the single most important thing you can do to let them share something of your working life. You can tell them all about it -- and it's important to do that -- but preschool kids learn about 90 percent by direct observation.

So many men have told me that the reason they haven't taken their preschoolers to work with them is that they think the kids won't be interested in what they see there -- just desks and files. But remember, your preschooler has probably never seen a desk or a filing cabinet before, and kids are interested in everything they see and in everything you do.

When Scott, 5, and Sissy, 3 1/2, visit their dad in the vast corporate office building where he designs billing systems for private interstate telecommunications hookups, they find a scene right out of "Star Wars"; mail is even delivered through the endless corridors by a kind of robot.

A father of three preschool girls who works for a firm that creates computerized medical information systems for hospitals told me how he takes his kids to the keypunch room where he works.

The most important part for them is simply being there and seeing what it's like. Very few kids can resist the allure of perfectly routine office supplies: pencils, pens, erasers, paper clips, staplers, tape, paper.

Make a quick inventory of the gadgets and machines in the place and let the kids have a go at them. Almost every office of any kind has a calculator that the kids can punch the buttons on without doing any harm. And don't forget the office copier -- which makes wonderful prints of children's hands.

It's always a good idea for a child on a visit to bring along a favorite book and a couple of small toys to fill in some time when you will be busy, and these can go in the copier, too.

The people you work with are another attraction. No matter how reserved and aloof they may act toward you, they will be curious and interested to meet your kids and will welcome them with smiles.

Getting to the place where you work can be more than half the fun, especially if you use public transportation.

A preschooler obviously can't be expected to stay contented through a day-long visit to an office, which in practical terms means that the visit will have to be on a day off -- and best on a weekday off, when there will be people and activity. Considering how much your child can learn about you through the visit, it's even worth a day of vacation time.

If your kids are shut out of the place where you work, take along a camera one day and shoot lots of pictures of the place. Have someone else snap shots of you actually doing your job.

A slide presentation of this will make a big impression on your kids, or they can have prints to look at whenever they like. If you work in a particularly noisy place, it might be fun to make a tape recording of the sounds of the place for the kids; the clatter of typewriters, the grinding of machinery. Business Travel

It's a good idea to keep kids abreast of travel plans, especially if your trip is going to make a major change in family routine.

You can include your child in family conversations about the trip, answer questions about it, and point out that Daddy will be gone for a few days (or a week, or whatever), but that Daddy will come home, just as he comes home every night from work. If you're flying or going by train, talk about airplanes or railroads; have the kids get out a toy plane, or read a bedtime story about a train.

Packing your suitcase can be another big deal that the kids can share.

If you travel regularly, there should be a picture of Daddy permanently posted in the kids' room or on the bulletin board or the refrigerator door. Even if you travel infrequently, it's a good idea to post a picture of yourself before you go.

I think the best reminder you can leave your kids is your voice on tape. If you simply turn on a tape recorder while you're reading a bedtime story one evening shortly before your trip, your child will have something of you to listen to over and over until you get back.

Postcards from a trip are hugely appreciated by kids; they're visible, physical proof that you remembered. If you're going to send them and have them arrive home before you do, you have to make it the first order of business on getting to your destination.

Should you always bring presents home from a business trip?

Many traveling fathers point out that a gift you bring home doesn't have to be expensive and it doesn't have to be a toy. If your kids are used to elaborate novelties and frequent gifts, you won't, of course, be able to fob them off little throwaway goodies you picked up. But most kids are absolutely delighted to get bars of hotel soap with the name of the place where you stayed on the wrapper.

Bring home the sturdy plastic dinner plates from the airplane; preschoolers will use them to mix paints, or to play a game of airline stewardess for replicas of the wings pins she and the pilot wear; many airlines supply these favors for child passengers and for kids who stayed home.

Kids of both sexes love little cosmetics presents; a can of shaving cream from Dad goes at the top of this list. Other surfire hits: a stick of flavored lip balm; a small plastic bottle of hand lotion; miniature tubes of toothpaste; new toothbrush; toothbrush holder; sunglasses.

The stationery section is a gold mine for small presents. Every child loves to get a small ring-bound notebook; a 2-year-old will scribble in it and enjoy ripping out the pages, and a 6-year-old may cover every page of it with pictures and words. Preschoolers love to have their own envelopes to stuff and lick. In fact it's hard to go wrong with any type of stationery supplies.

And for the last-ditch quickie presents, you can always grab a package of Life Savers, or hand-deliver an accordion fold-out postcard that will show where you've been.

It really isn't the present that counts -- it's the thought behind it. But a present is proof of the thought. And for a preschooler, it may be easier to understand the thought by way of a small object, than by way of an abstract explanation like "I really missed you, kid."