Or you may believe that what you are doing or observing is so un important that it is not worth recording. You are wrong on both accounts. Therefore, you must, in the practice of good science, maintain a record of all your experiments and observations while conducting a scientific investigation. Generally, this means maintaining a notebook for all lab and field activities. Writing lab reports and scientific papers from well-written lab and field notebooks is much easier than trying to recall what you did last week.
Lab notebooks are generally the size of tabloid paper.
Field notebooks may be smaller. Pencils are preferrable because errors can be corrected more easily. Also, lead is not affected by moisture. Therefore, it should be written legibly. Lab and field notebooks are frequently read by others, and should be written with that in mind.