 
 <prompt> Which one happen later, the single-grain experiment or the discovery say the amino acid tryptophan dey help mice well-being? Given di last question, write one context wey contain di answer. E fit be 1 - 20 sentences. Context: <response>: For early 20th century, Carl von Voit and Max Rubner bin measure caloric energy expenditure for different animals, using physics principles for nutrition. For 1906, Edith G. Willcock and Frederick Hopkins show say amino acid tryptophan dey help mice well-being but e no dey guarantee their growth. For middle of twelve years wey dem dey try isolate dem, Hopkins talk for 1906 lecture say "unsuspected dietetic factors," apart from calories, protein, and minerals, dey needed to prevent deficiency diseases. For 1907, Stephen M. Babcock and Edwin B. Hart do single-grain experiment wey take almost four years to complete. 