This book is based on an exploratory, descriptive and interpretive study which investigated interactions among learners' and teachers' conceptions of the nature of scientific inquiry (NOSI) and teacher instructional practices when teaching investigations in Physical Science. Learners' and teachers' conceptions on six NOSI tenets were investigated. These tenets are: difference between laws and theories; difference between observation and interpretation; there is no one method in science; accurate record keeping, peer review and replicability in science; socially and culturally embeddedness nature of scientific knowledge; and the role of human creativity and imagination in the development of scientific knowledge. Learners' NOSI conceptions were found to be inconsistent, fragmented and fluid. Teachers were found to hold mixed NOSI conceptions ranging from static, empiricist-aligned to dynamic, constructivist-oriented. Teacher instructional practices were found to be a repertoire of contrasting methodological approaches lying along a continuum ranging from close-ended to open-ended inquiry. Recommendations and implications for the practice of science education are raised and discussed.