An automatic analysis system for in vitro diagnostics, comprising: - a plurality of reaction cuvettes each comprising a base and intended to contain biological liquids samples to analyze, - a storage device configured to store the plurality of reaction cuvettes, - at least one samples processing station (44, 57, 64, 68), comprising at least one receiving cavity (48, 59) configured to receive and house at least partially one reaction cuvette, the at least one receiving cavity (48, 59) comprising a lower introduction opening (49, 60) which opens downward and which is configured to enable the introduction of a reaction cuvette into the at least one receiving cavity, and - a displacement device configured to displace a reaction cuvette, the displacement device being further configured to unload a reaction cuvette out of the storage device and to load and unload a reaction cuvette into and out of the at least one receiving cavity (48, 59) of the at least one samples processing station (44, 57, 64, 68) via the respective lower introduction opening (49, 60), the displacement device being disposed under the at least one samples processing station and comprising: - a first support element movably mounted according to a first direction of displacement which is substantially horizontal, - a second support element movably mounted on the first support element according to a second direction of displacement which is substantially horizontal and whish is substantially orthogonal to the first direction of displacement, and - a drive member movably mounted on the second support element according to a third direction of displacement which is substantially vertical, the drive member being configured to cooperate with the base of a reaction cuvette and to transmit a drive movement to said reaction cuvette. - a plurality of reaction cuvettes each comprising a base and intended to contain biological liquids samples to analyze, - a storage device configured to store the plurality of reaction cuvettes, - at least one samples processing station (44, 57, 64, 68), comprising at least one receiving cavity (48, 59) configured to receive and house at least partially one reaction cuvette, the at least one receiving cavity (48, 59) comprising a lower introduction opening (49, 60) which opens downward and which is configured to enable the introduction of a reaction cuvette into the at least one receiving cavity, and - a displacement device configured to displace a reaction cuvette, the displacement device being further configured to unload a reaction cuvette out of the storage device and to load and unload a reaction cuvette into and out of the at least one receiving cavity (48, 59) of the at least one samples processing station (44, 57, 64, 68) via the respective lower introduction opening (49, 60), - a first support element movably mounted according to a first direction of displacement which is substantially horizontal, - a second support element movably mounted on the first support element according to a second direction of displacement which is substantially horizontal and whish is substantially orthogonal to the first direction of displacement, and - a drive member movably mounted on the second support element according to a third direction of displacement which is substantially vertical, the drive member being configured to cooperate with the base of a reaction cuvette and to transmit a drive movement to said reaction cuvette.