Social and solidarity economy (SSE) is a field of economics based on co-operatives. But what do we know about it? I had the same question about 6 months ago but now, I can easily say that I know about it. Do you know about SSE? If you don't, come along to discover. I hope that this magnificent journey I did to the wonderful world of solidarity, economy and mathematics to cause to you in person the same interest that caused to me.