Amber started formatting 55-40 million years ago (during Cenozoic and Paleocene periods). The amber-full woods grew in the southern and middle part of what is now Scandinavia and in the adjacent areas of the Baltic Sea bottom (the Baltic Sea started formatting around 13 thousand years ago). Coniferous woods grew in this territory and from their resin amber was formed.

In XIX and XX centuries most scientists stated, basing their statements on research of the inclusions found in amber, that the habitat of the amber-full woods is far greater, because the insects and plants found in amber are typical to tropical regions and flora and fauna from different climate zones can't co-exist in the same area.

Scientist O. Her when explaining in 1869 how plants and animals typical to tropical and middle climates appeared in amber, stated that amber woods spanned through a huge mountain range covering areas from Scandinavia to Middle Europe and rivers from all of these areas carried amber with insects and animals to the sea, thus the variations in amber inclusions found in one place.

H.Konvent in his 1890 work „Monograph about amber" wrote that amber woods were dense, humid, dark and on their southern edges warmth-loving and even tropical plants grew. According to him almost all the trees were diseased. They were crippled by insects, parasite fungus, plants and various natural disasters (storms, thunders, fires, falling trees). While being constantly crippled these trees produced much resin which formed amber.

In 1915 the researcher of amber inclusions V. Vyler, while researching amber pieces with several or more inclusions, noticed that each of them contains insects of tropical and moderate climates. The scientist explained this fact – at the time of amber formation the tropical climate changed into the moderate one, thus the fauna is relict.

After summarizing previous scientists'researches of insects, in 1942 an analyst of amber fauna K. Anders formulated a hypothesis that amber forests grew on mountains. On mountaintops and on north sides coniferous trees grew and warmth-loving trees – on the mountain bases and southern parts, that's why, according to the author, insects of various climate zones are found in amber.

Later amber inclusion researches regarding its varietal composition proved that the insects and plants specific to tropical and moderate climate zones existed simultaneously. This fact is explained by the researches of amber and climate: it's very hard to distinguish such climate zones typical today at the period of amber formation (paleogenic period). Climate research shows that during paleogenic period variations in temperature weren't apparent, so they didn't have much significance on the spread of flora.

During the growth of amber forests the climate was warm (average yearly temperature was around +20° C) and very humid. It's stated that it was very similar to the Mediterranean sea climate type characterized by apparent wet and dry seasons. The researcher of European climate during the paleogenic period V. Sinycin pointed out that at the present territory of Poland and Germany evergreen flora with a large addition of sub-tropical coniferous and deciduous trees was spread.

This zone reached Scandinavia where coniferous and broad-leaved deciduous flora dominated. Mediterranean plants (bayberry, mirth, palms) took second place there and coniferous trees were present from both moderate and sub-tropical climates. These circumstances explain the coexistence of various species and their integrated appearance in amber pieces. Current climate zones became clearer only after the amber formation processes were over.

The biggest part of amber forest grew in lower plain or a little hilly relief because insect species living in still water or swamps predominate in amber pieces. Only a very small part of the inclusions show that amber forest grew in mountainous regions. It is believed that this was the western-most part of the amber forest habitat.

There were many swamps, big deep lakes, numerous rivers and streams in the amber forest. The soil was similar to current tropical forest soil type. Amber forests grew on carbonaceous and sandy soil. The soil contained much humus, but it also was well aerated and drained. The forest floor was constituted of wood mould, leaves, thorns and continuous moss covering. On warm and damp climate conditions these remains decomposed rapidly and the decomposed remains were spread by atmospheric rainfall. Oxygen penetrating lower soil layers determined oxidation processes.

It's believed that amber forest was very similar to today's Eastern Asian sub-tropical forests – very dense and dark at parts. Many various species of trees, bushes and other plants grew there. Those were the gigantic sequoias (50-80 m), oaks, chestnuts, many coniferous trees, many maples, fig trees, cypress family coniferous trees, small trees and bushes, dwarf palms and lianas. Moss, ferns and graminaceous plants rallied around the edges of the forest.

Amber trees grew in groups on higher areas and a big part was interblended with other trees. They grew on the edges of the forest, coasts of rivers and lakes and on mountain slopes. For this reason insects living in rivers and lakes are found together with forest plants in amber. Warm and very moist climate stimulate and intensive growth of fungus and other cryptogam plants which influenced changes in resin. Amber forests were populated by many sorts of insects, birds and mammals.

During the growth of amber forests the climate was warm (average yearly temperature was around +20° C) and very humid. It's stated that it was very similar to the Mediterranean sea climate type characterized by apparent wet and dry seasons. The researcher of European climate during the paleogenic period V. Sinycin pointed out that at the present territory of Poland and Germany evergreen flora with a large addition of sub-tropical coniferous and deciduous trees was spread.

This zone reached Scandinavia where coniferous and broad-leaved deciduous flora dominated. Mediterranean plants (bayberry, mirth, palms) took second place there and coniferous trees were present from both moderate and sub-tropical climates. These circumstances explain the coexistence of various species and their integrated appearance in amber pieces. Current climate zones became clearer only after the amber formation processes were over.

The biggest part of amber forest grew in lower plain or a little hilly relief because insect species living in still water or swamps predominate in amber pieces. Only a very small part of the inclusions show that amber forest grew in mountainous regions. It is believed that this was the western-most part of the amber forest habitat.

There were many swamps, big deep lakes, numerous rivers and streams in the amber forest. The soil was similar to current tropical forest soil type. Amber forests grew on carbonaceous and sandy soil. The soil contained much humus, but it also was well aerated and drained. The forest floor was constituted of wood mould, leaves, thorns and continuous moss covering. On warm and damp climate conditions these remains decomposed rapidly and the decomposed remains were spread by atmospheric rainfall. Oxygen penetrating lower soil layers determined oxidation processes.

It's believed that amber forest was very similar to today's Eastern Asian sub-tropical forests – very dense and dark at parts. Many various species of trees, bushes and other plants grew there. Those were the gigantic sequoias (50-80 m), oaks, chestnuts, many coniferous trees, many maples, fig trees, cypress family coniferous trees, small trees and bushes, dwarf palms and lianas. Moss, ferns and graminaceous plants rallied around the edges of the forest.

Amber trees grew in groups on higher areas and a big part was interblended with other trees. They grew on the edges of the forest, coasts of rivers and lakes and on mountain slopes. For this reason insects living in rivers and lakes are found together with forest plants in amber. Warm and very moist climate stimulate and intensive growth of fungus and other cryptogam plants which influenced changes in resin. Amber forests were populated by many sorts of insects, birds and mammals.

Volatile terpene full sap (transparent, colorless fluid with pine smell that is constituted of carbohydrate found in sap) constantly seeped to the tree's surface. Here it was influenced by lower pressure so it became less soluble; the volatile terpenes were evaporating quickly because of environmental influence. In sap that was on the sunny side the terpenes evaporated quicker. From its gas many small bubbles formed and the sap got clouded. Gas bubbles moved in the liquid sap, joined one another so semi-transparent or cloudy sap zones appeared. In dense sap the bubbles stayed small, densely scattered, so clouded, yellowish or even white sap areas appeared.

The thick sap slowly flowed down the tree trunk different color and denseness zones mixed creating amber with various patterns and colors.

After most of the terpenes evaporated the sap melting temperature increased, so sun heat couldn't melt them anymore. The sap stuck to the trunk and totally hardened. All colors that appeared during the flow stayed and can be seen in amber. Sap that was evaporating very quickly in sunlight became foamy and formed the very common porous foam amber.

Terpenes from seeping sap that was in shade evaporated very slowly, so this sap hardened slowly and stayed clear. Oxidation process that was especially intense because of light, heat and ozone effects also had influence on the color of amber. The color of amber affected by oxidation is much darker than that of inner formed amber.

Microorganisms, organic and mineral acids and humidity didn't participate in the processes of this stage. Amber form sap changed a little differently. It's shown by the physical features and chemical composition. This sort of amber is very bright, sometimes even colorless because the sap didn't react with oxygen (there was no oxidation process). Terpenes didn't evaporate so the amber contains almost all the volatile components that reacted with other constituents, thus this sap is very clear.

1. Cortical amber

This is the most spread and varying morphological variety of amber (58%). The sap flowing onto the surface of the trunk created large clusters that slowly oozed down. They melted and hardened again while heated by the sun. Because of the heat volatile components evaporated, though because of the viscous sap mass not all gas was able to evaporate. Various currents mixed together when the sap was flowing down the trunk, so this outer amber is of various colors.

Cortical amber can be from few centimeters in size to big pieces weighing several kilograms.

Cortical type amber pieces are thick, on a transversal cut they're convexed, with oval front part, with uneven longitudinal surface, when looking sideways it reminds a loaf of bread. The bottom and concaved part is usually with apparent or less noticeable pine bark marks. The convexed surface is variously carved – usually with grove of irregular forms that formed when the sap oozed in various directions or over gaps, hollows that remains from the pine plates, branches and other remains. Much rarely its surface is even or rippled. Sometimes in this resin carbonated bark plate remains or their imprints can be found.

Even thin plates, long flattened cylindrical trickles sometimes occur. The form of the cortical amber depends on the sap's flow width and form, the viscosity of the sap, the speed of the flow, the surface of the trunk and other influences.

2.Cortical sap flow

Timber resin lenses were formed inside the sap vessels inside the tree trunk. When the pressure grew inside the sap vessels, the pressured sap expanded the timber tissue, damaged the sap vessel walls and the resin flowed out easily. Cortical lenses are transparent and light-colored, because the resin that forms it was under pressure and isolated from the outside environment. There are no prints on the surface or inclusions. It's a very transparent, yellowish, without any impurities, oval, correctly shaped amber.

3. Sub-cortical sap flow

Sub-cortical sap lenses were formed under the bark when because of the pressure longitudinal and transversal vessel ruptured. The resin flowed under the bark, tore it of timber and the vessels formed there. Sub-cortical amber like the cortical one is clear and yellowish, thin (no more than 3 cm), though sub-cortical lens' surface always has cambium fiber prints.

4. Bark amber

Bark amber is formed in the thick amber tree bark when its planks separated.

This type of amber is clear and light colored, of unique and uneven form, cut edges that were formed by the contours of the separated tree bark plates. The archetypal bark amber characteristic is bark prints on both sides: bulging on one side and on the other side concaved. Bark amber plates can be from 5 to 15 cm length, 4-7 cm wide and 0.5-3 cm thick. Organic inclusions aren't found in them.

5. Micro-trickles – is "amber inside amber". They're first resin portions that flowed out and were conserved in macro-trickles – they're also rudiments of big trickles. They're created of thin (1-3mm thick) trickles, usually with a drop at the end, sometimes even the whole chain of such drops can be found. Micro-drops are of similar descent – clear amber drops that detached themselves from the tops of the trickles.

6. Macro-trickles – it's clear, layered amber that formed when resin periodically oozed out of the damaged tree part. Macro-trickles – the main containers of plant and animal remains, more than 95% of all inclusions are found in them.

The trickles were hanging on think (2-8 cm diameter) branches with sap coming out of them. There are many trickles that were attached to flat surfaces such as tree trunk or base of the branch. Most common trickles are cylindrical, 20 cm long or even longer and 2-3 cm in diameter. Completely intact trickles are never found, only their fragments, as they were broken while flowing down rivers.

Amber trickles – only clear amber. The yellow color of amber is because of oxidation and is darker than inner varieties of amber. They can contain gas bubbles and their clusters that are sometimes filled with water.

7. Amber drops

Amber drops are excess resin that detached from the trickles and the sap flows of the trunk. This morphological variety of amber is the most interesting by the variety of forms and the formation processes. Two types of amber drops are distinguished – clear and unclear amber drops.

Clear amber drops are little and clear like trickles. The biggest drop found is 1.5 cm in diameter. The drops are rarely found because they were quite small and after oxidizing disintegrated in initial clusters on the forest soil. They're deformed (mostly flattened), because the liquid drop hit the ground while dripping of the trickles.

Unclear amber drops have various morphological characteristics. It's always cloudy, from whitish to brightly white color and formed from very viscous resin. Sometimes foam shaped amber drops are found, their color isn't uneven and without and patterns. Average size of the unclear amber drop is 2.5-3 cm, though sometimes 5-10 cm drops can be found.