This dissertation study investigated the efficacy of a supplementary preschool embedded multimedia curriculum that was designed to increase one type of conceptual knowledge: taxonomic categories. Named the World of Words (WOW), this curriculum focused on teaching the properties and concepts associated with seven taxonomic categories and providing children with the vocabulary that is paired with these concepts. Participants were 178 low-income preschoolers (89 in the treatment group, 89 in the comparison group) taught by twelve preschool teachers. Six teachers implemented the supplementary curriculum with children in their classrooms four times per week for four months. The other six teachers went about their typical daily routines with for those four months, thus acting as a comparison group. Children in both the treatment and comparison groups were assessed on their conceptual knowledge and vocabulary knowledge before the study began, immediately following instruction around each taxonomic category, and at the conclusion of the study. Hierarchical Linear Modeling (HLM) was used to analyze data from these assessments. Findings indicated that children who experienced the curriculum acquired both the vocabulary and underlying concepts that were taught in the curriculum. In addition, they were able to transfer the conceptual knowledge they acquired to new learning situations, an initial indication that learning vocabulary embedded within the concept of taxonomic categories has the power to foster future learning. However, four months of this type of instruction was not sufficient to increase the growth of general receptive or expressive vocabulary knowledge. Results from this study support the notion that teaching conceptual knowledge and vocabulary in taxonomic categories is a powerful way to increase vocabulary and conceptual knowledge before children enter formal schooling. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]