This qualitative multiple case study explored the conceptual frameworks of two congenitally blind male adolescents on the nature of matter. We examined participants' responses on four tactile investigations focused on concepts and processes associated with matter changes. The matter changes investigated were dissolution, chemical change, expansion, and condensation. Individual interview and model-making sessions comprised the primary data collection, whereas journal writing and focus group interviews provided additional, secondary data. Participants' responses during matter activities were analyzed by using three data frames: structural views of matter, types of understanding of matter changes, and conceptual consistency of students' explanatory schemes. Coding of the responses identified macro- (physically observable) and microparticulate (invisible) views of matter and both scientifically accurate and alternate understandings of matter changes coexisting within one response set. Data analysis led to the development of individual meandering mind maps as an analytical tool that illustrates the shifting of each participant's thinking between the macro- and microparticulate views of matter. A meandering mind map utilized in the study consists of a macroparticulate outer layer, microparticulate inner layer, and an interface layer that includes lynchpin concepts compound, molecule, atom, and element. The lynchpin concepts are perceived to mediate and scaffold cognitive shifts between the macroparticulate and the microparticulate views of matter. During individual interviews, each participant's responses were coded to one of the three categories, plotted in clockwise sequence and connected with a line. The findings include that congenitally blind participants hold (a) both macro- and microparticulate views of the nature of matter, (b) scientifically accepted and scientifically alternative understandings about matter concepts, and (c) conceptually inconsistent explanatory schemes of matter across the four data collection activities. (Contains 3 figures and 2 tables.)