Teaching-learning transactions in subject areas falling under the umbrella of the 'hardcore-sciences' have been seen to be problematic because of a range of reasons. They could be problems as varied m vocabulary and technical jargon, to pre-conceived belief; structures andprejudices. In this connection the design factors of the SIMs should dejinitely take the experience of a classroom teacher into consideration. This article deals with the possible ways in which the teacher in a classroom can be transposed to the 'in built' teacher in the SIMs. The article presents a specgicpoint of view. One could take a positive or a sceptical stance towards it. We would welcome comments from those interested in the area of science teaching.