Question: how does blood vesselscommunicate with fat cells

Cheukyau (Jane) Luk answered on 25 Sep 2020:

Inside mammalian bodies, fat cells are closely linked with blood vessels. The blood vessels transport oxygen and nutrients into the fat cells and carry unwanted wastes away from the fat cells. Recently, scientists also find out two main ways in which the blood vessels do so: (1) to carry the items and give them to the fat cells, or (2) to squeeze themselves so that the items in the blood can squeeze through the gaps and be taken up by the fat cells.

To better illustrate the two ways described above, think about two adults (A and B) and one baby in a room. A is the blood vessel cell and B is the fat cell. The baby is any item that can be a nutrient or waste product.
In situation (1), A carries the baby and passes it to B. B receives the baby and plays with it etc.
In situation (2), A moves towards the wall and gives more space for the baby to crawl towards B. B then receives the baby and plays with it etc.

Hope the metaphor helps! Inside our bodies, A and B are more like a crowd of adults with two different backgrounds, the babies are things that can be actively produced by each of them or from other parts of the body (remember that the blood flows within the blood vessels and carries items throughout the body)!