Different students take differing approaches when placing the organs in the body. Some draw their organs directly on the body outline. Others draw them on separate pieces of paper and then stick them in position. Some groups are very particular about the details, so they create flaps and pop-ups in an attempt to show three dimensions. The greatest challenge of the design stage comes with the linking of the heart and other organs by blood vessels. Once they think that they have completed the task of connecting up all the organs, the students are given a set of counters that represent different kinds of molecules, in particular oxygen carbon dioxide, glucose a urea. They have to be able to move these counters around the body from organ to organ. through the heart and the lungs. using the appropriate blood vessels. It is an unusual group that does not have major problems at this stage, particularly with the connections between the heart and lungs. Despite all the work they have put into their model it is not until they have to use it that most groups realize that most organ to organ movement involves the pulmonary circulation. It is vital to the learning process that the students are allowed to make mistakes in the construction of their bodies and that the teacher resists the urge to take control in the solution of their problems, They need to be encouraged to think first and then construct good questions to ask their peers or the teacher