Research on the role of computing in the understanding of scientific phenomena shows that the carrying out of experiments with software is complementary to their realisation with respect to reality, but is not sufficient (Nonnon, 1998; Vivet, 2000; Smyrnaiou and al. 2003; Guichard and al., 2004). This is all the more true for young children, for whom confrontation with material objects is necessary. In the context of scientific interactive exhibitions - which are today considered as real places of formal learning in the framework of science education - the use of software alone, for purposes of understanding, is sometimes necessary in order to show natural phenomena or technical systems, that are impossible to display in real forms (Guichard, 1987; Van-Praët, 1988). We thus wanted to determine, in the context of a visit to a scientific exhibition, whether the use of specific simulation software by children allowed them to acquire knowledge concerning the physical world. This research goal gives rise to two questions concerning on one hand, the contribution of such computer environments on a cognitive plane for children who manipulate them, and on the other hand the role of the adults accompanying children during such activities. We carried out research in an exhibition for children aged 3 to 5 years old ("Children's corner") in the Cité des sciences et de l'industrie (Paris, France). We based our work on the particular case of an interactive exhibit proposing activities around painting using a software environment. By means of a tactile interface, young children are invited to draw with their finger by making mixtures of colours. Two series of observation were carried out, firstly in an experimental context of manipulation, then in a natural context, with the objective of evaluating whether the use of the simulation software by the children allowed them subsequently to make the suitable mixtures in order to obtain definite colours. The children were filmed and the recordings were completely transcribed The first study concerned 20 children aged between 2 years 6 months and 5 years 6 months observed in an experimental context of software manipulation, under the control of the same expert tutor, an educator of the exhibition. The analyses, aiming at identifying the age from which the children were able to implement procedures acquired by means of the simulator in favourable conditions of scaffolding, highlight that for the considered field of knowledge, the age of 4 years age appears to constitute a transition. The second study therefore concerned 25 children aged at least 4 years old observed in the usual context of use, accompanied either by one of their parents or by an educator of the exhibition. The pre-post test comparison of their actions with the software, consisting in solving a problem of mixture of paintings with material objects, allowed us to evaluate the contribution of the use of the simulator in both situations. In addition, in order to characterise interactions during the course of activity, a specific analytical model was developed: the media square. Analysis of the parent/child interactions showed that such tutoring seemed essentially connected to the informative contents of exchanges, relating to the field of knowledge involved. In addition, the simulation activity seemed to have mainly the function of a formal exercise for the young user.The results showed that the use of simulation-type devices, displayed in scientific exhibitions, can allow the acquisition of knowledge on the physical world, but that it depends on two conditions: the previous experience of the child and also the tutoring quality of the adult accompanying the child during use of the simulation. This last point raises the question of the adult's help in the child's conceptualisations, from the point of view of discourse, but also in the use of the software, on the level of manipulation. GUICHARD, J. (1987). Modèles et simulation en situation muséologiques pour les enfants. In A., Giordan, et J.-L., Martinand, (Éds.). Modèles et simulation, Actes des "Neuvièmes journées internationales sur l'éducation scientifique". Chamonix, février 1987. Paris : Université Paris 7.GUICHARD, J., LECHAUDEL, A., & MANGEOT, N. (2004). L'expérimentation directe à l'heure du multimédia. La lettre de l'OCIM, 91, 4-10. NONNON, P. (1998). Intégration du réel et du virtuel en sciences expérimentales. In F.-M., Blondel, et M., Schwob, (Éds.). Actes des "Huitièmes Journées Informatique et pédagogie des sciences physiques" (pp. 133-138). Montpellier, mars 1998. Paris : INRP. SMYRNAIOU, Z. (2003). Modélisation : L'apport des logiciels éducatifs. Thèse de doctorat, Université René Descartes - Paris 5.SMYRNAIOU, Z. & WEIL-BARAIS, A. (2003). Cognitive approach of two technology based learning environments of modelisation and simulation intend to a scientific education. In 3rd IEEE International Conference on Advanced Learning Technologies, Athens, July 9-11. VAN-PRAËT, M. (1988). De la galerie de zoologie à la galerie de l'évolution, vers un musée du quatrième type. In A., Giordan, et J.-L., Martinand, (Éds.). Communication, éducation et culture scientifiques et industrielles, Actes des "Dixièmes journées internationales sur l'éducation scientifique" (pp. 395-399). Chamonix, 1988. Paris : Université Paris 7.VIVET, M. (2000). Des robots pour apprendre. Sciences et techniques éducatives, 7, 1, 17-60.