An embryonic stem cell is a cell that can differentiate into any type of tissue. what is the latest stage in which you can find embryonic stem cells?

The last stage of embryonic development where the embryonic stem cells are found is the blastocycst. In this stage the cell differentiates and group themselves into different body parts and specialized cells. This stage is reached with in the period of 3 to 5 days of the embryo development.

sodium i think the chemical element of atomic number 11, a soft silver-white reactive metal of the alkali metal group.

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added