We tend to think that goods and services on the scale of a human body can only be provided by machines the size of us. Or larger. That has been the case up to now, because machines were operated by people. We cannot manipulate tiny machines. And because power supplies and robotic controls were large. This may not be the case in the future, especially with cold fusion.
In suburban Atlanta, when you want to remove a large tree, they send men with chainsaws and a giant, noisy machine the grinds branches into wood chips. They sometimes send a bulldozer machine with giant claws. Everything is big. So, do you need big, heavy equipment to grind a tree into sawdust? Nope. Thousands of trees every day are ground up by tiny machines: ants. In the future, when cold fusion power supplies can run a machine continuously for years, we may have robotic tree-removal ants. Millions of them will be dispatched from the tree service building. They will fly to your house, swarm over the tree, and take itty-bitty bites out of it, starting at the top. Each one will fill up a small container, like a stomach, and fly back to the tree service building. A continuous stream of them will keep working until there is nothing left of the tree.
Ants work from the base of the tree, making it fall over after a while. Robotic ants will work from the top. They will be supervised by a person or by a larger, much smarter robot that understands physics, the center of gravity, and which leaves and branches should be disintegrated first to prevent the tree from falling onto your house.
Many other tasks might be done with large numbers of small machines, such as building roads, or recycling landfill garbage that has been in the ground for a century.