 Recently, accounts of explanation revolving around  “mechanisms”  have been widely discussed (e.g., Baetu 2015, Bechtel 2006, 2008, Bechtel and Abrahamsen 2005, Craver 2006, 2007, Darden 2006, Glennan 1996, Machamer et al. 2000). Many philosophers view experimental biology as fundamentally concerned with the discovery of mechanisms (Craver and Darden 2013, Darden and Craver 2002, Tabery 2004), where mechanisms are understood as akin (though not equivalent) to machines with interconnected, organized parts operating to produce regular or expected outcomes. Conceiving of biological explanation in terms of mechanisms provides a philosophical framework that closely tracks biological practice and does not rely on the notion of a theory. Besides providing new models for explanatory reduction  (Section 3.2),  mechanisms also have been used to demonstrate integration among different fields. Darden (2005) argues that both reduction and replacement fail to capture the relations between classical and  molecular genetics.  Both fields deal with different mechanisms that occur at different periods of the cell cycle and involve different working entities: classical genetics focuses on meiosis and involves chromosomal behavior; molecular genetics focuses on gene expression and involves various molecular entities such as nucleotide sequences. Relations between the two fields are manifested as differential attention to distinct aspects of a larger, temporally extended mechanism.