Need at least as many vectors as coords (dimensions) to span: 

In the R³ (3rd dimension)  

• If we have one vector, at most we can get a line
• If we have two vectors, at most we can get a plane
• If they are the same two vectors then they will be the same line and therefore not form a plane. 
• If we have three vectors, at most we can span all of R³
• If all three vectors are the same then we would have a line
• If two of the three vectors are the same we will get a plane
• If we have more vectors than dimensions when you row reduce you will get a row with 0, 0, 0.