What is left at the end of the day?

When leaving the work, I met a former student who was very excited rebuilding a computer that was developed in our school in 1971. Although he must be born in the 1990's, he was very glad to recover some glory from a long time ago when our school was creating some kind of Brazilian technology. 

Minutes later, I took this photo above Pinheiros river when coming back:

what made me ask: what is left at the end of those days when some professors were very proud creating a new thing? There are some dissertations in the library that nobody is reading today. I told to the former student that a project that began in our school around 1975 finished around 1990 just because the manager decided to focus on what was essential to make it work, abandoning a lot of implementations that would be used to write thesis. Thus, what is left at the end of some decades of work? Almost nothing. The main question however is what will be left at the end of my life? I am really afraid that even this blog will be useless. Now I understand that only what I offer to the Lord will be kept at the end of my life.