What is the fine-grained topic of the following text: Weights of male offspring were recorded at birth and 7 weeks of age (adulthood), at which point lungs were fixed for morphometry and stereology (n = 6/group), or bronchoalveolar lavage fluid (BALF) was collected for cell counts (n = 6/group). Only return the topic.
Recording and analyzing physical and biological data of male offspring at birth and adulthood