17695
However , key to realizing this potential requires a strong understanding of stem cell biology , techniques to maintain stem cells , and strategies to manipulate cells to efficiently direct cell differentiation toward a desired cell type .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None