Man has always to be busy with his thoughts if anything is to be accomplished.

Antonie van Leeuwenhoek

My work, which I’ve done for a long time, was not pursued in order to gain the praise I now enjoy, but chiefly from a craving after knowledge, which I notice resides in me more than in most other men.

Antonie van Leeuwenhoek

I've spent more time than many will believe [making microscopic observations], but I've done them with joy, and I've taken no notice those who have said why take so much trouble and what good is it?

Antonie van Leeuwenhoek

Whenever I found out anything remarkable, I have thought it my duty to put down my discovery on paper, so that all ingenious people might be informed thereof.

Antonie van Leeuwenhoek

I observed certain animalcules, within whole bodies I saw so quick a motion as to exceed belief.

Antonie van Leeuwenhoek

They were about the size of a large grain of sand, and their bodies being transparent, that the internal motion could plainly be seen.

Antonie van Leeuwenhoek

I have divers times endeavoured to see and to know, what parts the Blood consists of; and at length I have observ'd, taking some Blood out of my own hand, that it consists of small round globuls driven through a Crystalline humidity or water.

Antonie van Leeuwenhoek

I saw this vast number of animalcules not all through the semen, but only in the liquid matter adhering to the thicker part.

Antonie van Leeuwenhoek

I saw in the body of one of these animalcules a bright and round corpuscle, placed near the head, and in which a very wonderful swift motion was to be seen, consisting of an alternate extension and contraction.

Antonie van Leeuwenhoek

In the year 1657 I discovered very small living creatures in rain water.

Antonie van Leeuwenhoek