How does a beehive work?

Once you have the idea that a beehive is just a pile of boxes with rows of wooden frames hanging inside them for the bees to do their own wax comb building, you are almost there.
Hives used to be big baskets but the problem was how to get the honey out and how to alter the size when the colony of bees grew too big for the space.

This was solved back in the mid 19C when the first movable frame hives were invented. They are made from a pile of topless, bottomless boxes sandwiched between a floor and a roof. Key to the whole idea was having all the parts of the same standard sizes, so that any box or any frame could be swapped with any other box or frame. This meant that you could take away a box that was filled with honey and put an empty one or more in its place. You could also re-arrange the frames and change them round or remove one at a time to get the best results.
An important incidental advantage was that you could inspect every part of the hive without destroying anything and put it all back in exactly the same order. Because of this, new possibilities arose for managing the bees, controlling their diseases and dividing a colony to make two or more new ones.

The new movable frame hives would not have worked but for the discovery of what we call “bee space”. This is a gap of about 4mm between every part and every other part. The frames hang on rails in such a way that their ends are a bee space from the walls, and their tops and bottom bars are a bee space away from the frames above or below. The bees respect this space. It is what they need to get around inside the hive. If you make it too narrow the bees fill the gap with wax or propolis resin, sticking the parts firmly together. And if you make it too wide the bees take the opportunity to fit in a few extra cells and this too glues the parts together. The Rev. Langstroth, an American clergyman, is credited with discovering this and building the first hives that took advantage of it. Most of the world still uses “Langstroth” hives, but in Britain a different, smaller, size, usually called “Modified National” was adopted as the standard. Nobody else uses this size!

The floor of a hive is made from boards with a rim round the edge on three sides to give the bees room to come and go and an entrance almost the full width of the hive. Older hives had legs but modern hives are placed on stands and have no legs, which makes them much easier to transport and simpler to build. In the winter, or if the colony is small, the entrance is often narrowed by putting in a block of wood with only a small door cut in it. Often in winter a special metal strip with holes too small for mice but big enough for bees is put in place. Mice can be serious pests in a winter hive when it is too cold for the bees to defend their property, so we try to keep them out.

The roof is simply a box that fits over the top, with a waterproof, usually metal, top surface. Water is a big problem for bees and a good roof is probably the most important part of the hive.
Usually directly under the roof there is a crown board that is simply a square of plywood with a rim that allows a bee space over the top of the frames in the top box. A crown board usually has holes in it specially for placing feeders in autumn. Feeders are a way of giving the bees sugar syrup to replace honey taken so that they have plenty of food to see them through the winter.

It’s a good idea to separate stored honey from developing brood with young bees in it. If they are mixed you have a problem removing honey without killing brood. The solution, another 19C invention, is the “queen excluder”. This consists of a wire grid or a metal sheet with many accurately measured holes in it. A queen bee is just a fraction wider than a worker and she cannot get through a queen excluder. Therefore all her egg laying happens below the excluder and all the space above, to which the workers can come and go easily, is used for honey storage with no eggs or larvae mixed in it.
One of the advantages of movable combs in frames is that the honey can be extracted in a centrifuge without destroying the wax comb. The frames of comb can be used over and over again, refilled by the bees without the need to rebuild all that expensive wax.

There are many minor variations on the theme described above, from special entrance boxes that collect pollen from the homecoming workers to top bar hives where the combs hang from simple wooden bars that form the roof to a long box on legs.
Historically there have been bees kept in every possible container from sawn-off hollow tree trunks to walls made of pottery tubes and hollow logs hung from trees or houses. People have kept bees for thousands of years but the revolution came in the late 19th century when the inventions described above made the many new techniques of modern beekeeping possible.