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.
tˈɛknɪkəl ɐdvˈænsᵻz ɪnðə dɪvˈɛləpmənt ʌv ˌækɹoʊmˈæɾɪk lˈɛnzᵻz ɪŋkɹˈiːst ðə ɹᵻzˈɑːlvɪŋ pˈaʊɚɹ ʌvðə mˈaɪkɹəskˌoʊp ænd ɚɹˈaʊnd wˈʌn θˈaʊzənd ˈeɪthˈʌndɹɪd θˈɜːɾi nˈaɪn, mɐθˈaɪəs jˈækɑːb ʃlˈeɪdən ænd θiːədˈoːɹ ʃwˈæn aɪdˈɛntᵻfˌaɪd ðæt sˈɛlz wɜː ðə fˌʌndəmˈɛntəl jˈuːnɪt ʌv ˌɔːɹɡɐnᵻzˈeɪʃən ʌv ˈɔːl lˈɪvɪŋ θˈɪŋz.