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

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

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

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?

How inscrutable and incomprehensible are the hidden works of Nature!

Those who want to get wet need no umbrella!

The more we love our friends the less we flatter them it is by excusing nothing that pure love shows itself.

That a lie which is half a truth is ever the blackest of lies That a lie which is all a lie may be met and fought with outright - But a lie which is part a truth is a harder matter to fight.'

If you want to be right-sized in body, you've got to get rid of the supersize way of life.

The value of a promise is the cost to you of keeping your word.

If [Bush's] successors don't screw it up, within 10 years NASA will have us back to where we belong -- on other worlds.

Nerves just mean that you care.

No opinion that cannot stand discussion or criticism is worth holding.

As I am. As I am. All or not at all.

Love. It isn't very popular in technical circles to say a lot of mushy stuff about love, but frankly it's a very very important part of what holds our project together.