When I was a young researcher, just starting out, something happened that changed my life.
let's break down that sentence by identifying the parts of speech in each word ;
when : subordinating conjunction
I : pronoun
was : verb (linking verb)
a : article
young : adjective
researcher : noun
just : adverb
starting out : verb phrase (present participle phrase)
something : pronoun
happened : verb
that : relative pronoun
changed: verb
my: adjective (possesive adjective or determiner)
life: noun