Is histone the key to control gene expression?

No, histones are proteins that hold chromosomes together.  Other signals and pathways cause liver and muscle cells to differentiate in the embryonic state.

For example, retinoic acid causes stem cells to become neural cell progenitors.  With today's knowledge, no amount of coaxing can cause cells that don't see retinoic acid to become nerve cells.

There is quite a bit of scientific research going on trying to decipher a "histone code", that is, that a specific pattern of histones bound to DNA can serve as a signal to the cell that those DNA regions should be unfolded for transcription (gene expression), while others should not.  I'm not sure if this process is involved during development of tissues and organs,though.

During development, cells within the body receive signals that determine their cell fate.  These signals are transduced by the cell and lead to altered gene expression (genes that are expressed versus genes that are silenced).

How?  Some of the end products of this signal transduction are transcriptional activators/enhancers (which recruit histone acetylases(HAT)).  HAT alter "tails" of certain histones which causes them to "open up" the DNA that they hold.  You must understand that DNA in its condensed form around histones is hard to transcribe.  RNA polymerase and the basal transcriptional factors simply have a tough time getting to the promoter region.

Repressors may recruit histone deacetylases (HDATs).  Also, there is DNA methylation but that is a more permanent form of repression of gene expression.

I will give you an example:  in your body are erythroid progenitor cells (which arise from stem cells).  There are two paths they can take:  kill themselves(cell death) which happens in the absense of erythropoietin(Epo), or they can differentiate into red blood cells in the Presence of Epo (they are stopped from committing suicide).

When Epo (made by kidneys in response to low O2) binds to a cytokine receptor of the erythroid progenitor cell, this causes signal transduction.  One/some of the end products of this signaling pathway is/are responsible for turning on Bcl-xL, a gene that codes for a protein that represses cell suicide.

Throughout development and life this is how cells become to be what they are.  They receive signals from other cells at different times which "turn off" or "turn on" specific genes.

Histone is a part of gene transcriptional regulation mechanism. As an example, even when histone is methylated  and allowing other factors to access the DNA without a proper transcriptional regulator or promoter, the gene is not transcribed.
The differentiation of liver cells and muscular cells is another ball game. In this case, during developmental stage, embryonic cells differentiate into different type of cells based on the localized signals which can be growth factors, and cytokines allowing different types of proteins being made. The newly made proteins allowing cells to specialize in certain function and develop into different tissue.