The following extracted article was written by Ian Saaiman who is a bonsai and penjing grower.  It was prepared for a penjing demonstration at a bonsai club.  Assisted and photographs taken by Antoinette Pedro (FSRC).
A reflection of nature in a pot albeit a forest, landscape, land and waterscape, is one way of staying connected to the unseen forces of life.  The unseen life-force is in Chinese terms called “Chi” (Qi).  A mixture of rock, soil, moss, grasses and trees in penjing (living landscape in a tray or pot) consists of qi that is yang (trees, grasses etc.) and yin (rock, pebbles etc.)  The yin and yang forces are opposites but yet when balanced provide a comfortable state of existence, eg sea and seashore.  The sea is a yang force (which is affected by the phases of the moon and forces of nature) when compared to the placid beachfront.  If the sea is angry and stormy, the placid beachfront is hammered and sand is scattered by the sea.  This indeed is an imbalance when compared to a calm day, but nature is filled with yin and yang forces in both balanced and imbalanced state.  Although we have no control over the forces of nature, we can observe our own state of balance and we can attempt to restore imbalances.
A further point to observe are the aspects of heaven, earth and man.  Now, why involve these aspects when creating penjing?  From a basic point of view, a nature scene consisting of trees, moss and ground covers in a pot, uses a suitable soil mixture and requires watering on our part to survive.  In the natural world, a wood or grove would go through the natural cycles of growth, nutrition, decay and malnutrition without any interference by man.  Man's greed is often an unnecessary intervention i.e wood byproducts, estate development etc. which is a devastating imbalance.  If we look at the spiritual and metaphysical aspects
we should be able to observe the role of heaven, earth and man.  We need to look at the practices of religions of various old cultures to see that the earth was regarded as part of the spiritual devotions.  So getting connected with and understanding the balancing forces is obviously vital to creating penjing.  If we take a deeper look at oriental metaphysics and certain arts, we may find that heaven, earth and man concepts play a significant role.  Adding the Daoist concept of the path or the way, we have many seen and unseen “ingredients” before we actually start any work on penjing in a good and calm state of mind.
As we create penjing we also make use of the five elements for the following reasons:?wood - small trees which are planted?fire - sun which induces growth of trees, plants and mosses?earth - growing medium?metal - shears to prune roots and branches, wire to shape trees, nutrients absorbed from earth?water - survival of penjing  (also quenches our thirst on a hot day)
One needs to observe the natural world and its changing cycles.  One also needs to have a basic understanding of human nature and the way we have changing cycles.  The basic knowledge of horticultural practices and knowledge of the species of trees and plants to be used in penjing, goes a long way to ensuring a successful creation.  If we can do this in a calm and understanding manner as well as pushing ego aside, we can create penjing with a great spirit of interconnectedness and balance.
Brief explanation of specific words in penjing:?shumu penjing - tree penjing, tree in a tray or pot?shanshui penjing - landscape penjing, rock, trees and accent plants in a tray or pot shuihan penjing - water and land penjing, rock, trees and accent plants in tray or pot which may represent water by white sand or the white sections of a tray or pot used.