For example you have a cell or already a bunch of cells. Those cell(s) divide and after several week you have a grown organism, for example a human with limbs, several different organs etc. 
However, how do cells know where up, down, left, right etc. is?
I know left and right can be defined clearly in physics. However how do cells define those directions and what are mechanisms for them to grow into a certain direction? 
Is there a paper or a longer article dealing with that question/problem?

I don't think my knowledge on Biology goes far beyond high school level maybe 1. term at a university. If I have to, I would read and learn everything I need to know to understand the matter. 


Question: Responding to players paying exclusively with gold coins
Answer: Living high off the hog until the money wears out is a common theme in fantasy novels.  If you've ever read the Conan or the Fafhrd and the Gray Mouser series, this happens about every times the heroes come into money.  It's also not uncommon in real life.  How many times have you heard/read about movie stars or athletes that spend tons of money on non-essential items.

Here's a few outcomes of PC's spending money like water:


Merchants will start charging PC's more than list price for items.  If PC's start to complain, have the merchants start lying about the true value of the item (e.g., these are not just common X, these are imported from Y).
Invitations to join X.  This could be guilds, secret societies, nobility; but they will all have costs associated with them.  There will be an initial cost, but then they'll be others to continue to be in good standing with the association.
In a way, D&amp;D is based on PC's being able to purchase the magic items.  If your campaign is set-up differently, then you'll need to adjust the amount of wealth available to the PC's.  Instead of giving them coin, give them magic items that they don't need (e.g., an enchanted pole-arm weapon) or could use (e.g., book of vile darkness for good PC's); items not easily sold (e.g., artwork); items that are hard to transport (e.g., statues); and items that have inherit costs (e.g., deeds to lands currently occupied by monsters (or have outstanding debts).  Since the PC's are now the owners of the property, they are responsible for the damage/destruction caused by the monsters (or past taxes).)