How cells learn to become different in the newborn?

[GTOM]

So a new life borns. There is only one cell at the beginning. It starts to multiplicate. What tells its descendants, now you have to become liver, you have to become a neuron, you have to become skin?
How is it that the first generation of new cells learn that they have to be different from each other, while there arent already different cells around them? What makes the difference at the very first place?

 

[BillTre]

In animals, its a step-wise series of molecular signals to the developing cells at different particular times.

Its a very complex process. Lots of mutations have been found that affect different parts of of the early developmental process (indicating lots of different processes controlling lots of different sub-units of the whole).
Different signal control different aspects the developing plan of the developing body, in a step-wise manner. Different things happen at different times in development, or later life (like metamorphosis).

The signals can be generated from different sources such as: particular molecules stored only at one end of a embryo (such as anterior or posterior) providing a signal to cells ending up there they they should develop in a certain way. Other signals can involve signals among cells (usually, but not always biochemical) and cell location in the body. Decisions made by cells in this way can be either reversible or irreversible depending on which specific case you are looking at.
This great variety of processes makes it "easy" for evolutionary processes to generate not just the first differences in an embryos cells (probably a dorsal-ventral distinction), but a huge number of subsequent details of the final organism.

 

[Drakkith]

This is a very complex topic, GTOM, and one that is closely related to evo-devo (evolutionary developmental biology), as evo-devo offers us not only the chance to understand how the development of different organisms are related, but has also led to the discovery of many genes crucial to the development of humans and most other animals. Here are a few wiki links to get you started. They're a bit random and perhaps too technical to be of much help if this is your first time looking into the topic, but I hope you find them useful.

https://en.wikipedia.org/wiki/Evolutionary_developmental_biology
https://en.wikipedia.org/wiki/Evo-devo_gene_toolkit
https://en.wikipedia.org/wiki/Hox_gene
https://en.wikipedia.org/wiki/Pax_genes
https://en.wikipedia.org/wiki/Gap_gene
https://en.wikipedia.org/wiki/Hyalin
https://en.wikipedia.org/wiki/Lefty_(protein)
https://en.wikipedia.org/wiki/Deep_homology

 

[VIctor Medvil]

Well, It is all a long set of protein interactions and Gene Activations or Gene Deactivations, in general, that evolution over billions of years has gotten right or the offspring would not form correctly, which as you can imagine is a huge evolutionary disadvantage to have malformed offspring or the inability to reproduce usually causing extinction.

In the same way you can induce artificially Stem cells, then differentiate them into higher tissue types artificially with different chemical messagers, so too can the body with the correct protein/gene activation/deactivation, which produce those chemical messagers naturally. It is function of something called Swarm Intelligence in the body, which is vital for multi-cellular organisms smooth function, all stored in DNA sequences with the proper order to do these functions for a complete and successful organism construction.