This paper reports an investigation of biology students' discussion of knowing in work placements, as accounted in blogs. Twenty-two blogs, containing 78 individual entries, written in conjunction with a work placement course for students in a tertiary level biology program, have been analysed in the study (The blogs are publicly available here: https://biopraksis.w.uib.no). The aim of the paper is to increase understanding of how work placements shape biology students' personal epistemological trajectories. The analysis is performed by employing a theoretical lens that emphasizes the situated nature of knowing, as enacted in working practices. The blog accounts consist of the students' appraisal of their own learning and knowing in work placements, situated in biology undergraduate education. The investigation suggests that the students' personal epistemologies develop in an interplay with context and personal epistemologies to shape their trajectories toward biology knowing. These trajectories have been analysed in terms of their procedural, conceptual, and dispositional dimensions. The use of blogs as a data source is argued to be appropriate to analyse personal epistemologies. Other strengths and weaknesses of this design are discussed.