Cell specialization or cell differentiation as the name indicates, is the process during which cells become specified to perform specific functions instead of generic function.
The first cell that is formed after union of egg and sperm is called as Zygote that is not specified to perform only one function. It has all the genetic data of an organism and can develop into any specific cell with time. Zygote is an specialized cell.
When zygote keeps dividing, after 5 days it becomes a mass or around 300 cells called blastocyst that have two main layers- an outer layer of trophoblast and inner layer of stem cells. These stem cells can be further specialized into any type or cells or an organism.
After a time span of around two weeks, stem cells or inner layer of blastocysts further splits into three layers, ectoderm, mesoderm and endoderm. Now mesoderm is the layer which is later specialized into heart or muscle or bone cells.
Heart cells are the excellent examples of specialized cells that give the heart an ability to pump blood and make our survival possible.
Every person has their own part to play or if you want to get scientific then a niche. And if somebody doesn't do their job then it could slow everyone else down. Maybe I don't fully understand the question, But I hope its right.
