The smallest seed

Mark 4

30 Again he said, “What shall we say the kingdom of God is like, or what parable shall we use to describe it? 31 It is like a mustard seed, which is the smallest of all seeds on earth. 32 Yet when planted, it grows and becomes the largest of all garden plants, with such big branches that the birds can perch in its shade.”

https://www.guinnessworldrecords.com/world-records/66395-smallest-seed

The smallest seeds are those of epiphytic (non-parasitic plants growing on others) orchids, at 992.25 million seeds/g (28,129.81 million/oz) (cf. grass pollens at up to 170.1 billion grains/g or 6 billion grains/oz).