Look at these sentences:
Note that to express more and more [thing(s)] and less/fewer and less/fewer <thing(s)>, you will use de plus en plus de [chose(s)] and de moins en moins de [chose(s)].
Remember that the last de becomes d' in front of a vowel or a mute h.
See also Better and better, worse and worse = de mieux en mieux, de pire en pire (comparisons), De plus en plus and de moins en moins = more and more and less and less (comparisons with adjectives, adverbs, verbs) and Plus... plus..., moins... moins... = the more...the more..., the less...the less... (comparisons with phrases)
Here are other Comparative structures:
Making comparisons with adjectives: plus... que, aussi... que, moins... que
Making comparisons with adverbs: plus... que, aussi... que, moins... que
Making comparisons with verbs: plus que, autant que, moins que
Making comparisons with nouns: plus de... que, moins de... que, autant de... que
And Superlative structures:
Le, la, les plus and le, la, les moins = the most and the least (superlatives of adjectives)
Le plus and le moins = the most and the least (superlative of adverbs)
Forming the superlative of adjectives in complex cases
Meilleur, mieux, pire / plus mauvais, plus mal = better, best, worse and worst (irregular comparatives and superlatives)