Even with dramatic changes in women's workforce participation, the sexual division of labor in the family has remained essentially unchanged for many years. The first big change in the relationship between family and work occurred with the

Industrial Revolution

Explanation:

The first big change in the relationship between family and work that we find in history came with the Industrial Revolution. The Industrial Revolution led to a rise in factories and industry, and to the development of larger, busier cities. In these cities, women were able to find employment more easily, as the use of machines meant they did not have to rely solely on their physical strength. Moreover, as wages dropped, women often found employment to contribute to the family's budget. This change led to a complete revolution when it came to the role of women within their family.

a factory opens that mass-produces light bulbs.

explanation:

not sure if that's an answer to your questions but this is an example! : )

i believe your answer is mountains.