When Henry Ford developed the assembly line method to manufacture his black Model T cars, he revolutionised manufacturing through the segmentation of a whole job into a division of tasks. By standardising the product and breaking down the whole process into tasks, he could employ unskilled workers assisted by machines and moulds. In turn, workers are paid decently and hence can afford to buy the cars.
In economics, we say that the factors of production are capital and labour, and that economic growth comes from increases in quantity or from efficiency of these factors. Adam Smith in his pin factory analogy asserts that there are limits to specialisation and division of labour, and thus limits to reducing unit costs, unless there is innovation.