  Standard micro-economics concentrate on the description of markets but is
seldom interested in production. Several economists discussed the concept of a
firm, as opposed to an open labour market where entrepreneurs would recrute
workers on the occasion of each business opportunity. Coase \cite{Coase} is one
of them, who explains the existence of firms as institution because they reduce
the transaction costs with respect to an open labour market. Whatever the
rationale proposed by economists to account for the existence of firms, their
perspective is based on efficiency and cost analysis. Little attention is paid
to the dynamics of emergence and evolution of firms. The aim of the present
manuscript is to check the global dynamical properties of a very simple model
based on bounded rationality and reinforcement learning.
  Workers and managers are localised on a lattice and they choose collaborators
on the basis of the success of previous work relations. The choice algorithm is
largely inspired rom the observation and modeling of long term customer/sellers
relationships observed on perishable goods markets discussed in Weisbuch
etal\cite{Weisbuch} and Nadal etal\cite{Nadal}. The model presented here is in
no way an alternative to Coase. We describe the build-up of long term
relationships which do reduce transaction costs, and we deduce the dynamical
properties of networks built from our simple assumptions.
  In conclusion, the present model explains the metastability of employment
relations in the firm, but something has to be added to it to explain the more
efficient workload repartition observed in real firms.
