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Technical advances in the development of achromatic lenses increased the resolving power of the microscope and around 1839 , Matthias Jakob Schleiden and Theodor Schwann identified that cells were the fundamental unit of organization of all living things .
 Matthias Jakob Schleiden, Theodor Schwann
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Matthias Jakob Schleiden, Theodor Schwann