One of the most striking features of our Montessori areas has always been our low shelves. This set was handmade and purchased well before Otis was born. When putting together Otis' Montessori bedroom these low shelves were one of the first pieces of furniture we used.
Why does a newborn need low shelving? For consistency and order. From birth the infant knows and understands where their materials are kept. Otis' first toys and materials like rattles were kept in a basket on the bottom shelf. As soon as he could move he would go to his shelves for his materials.
From a very young age the child is learning to rely on and trust his environment - his materials are always in the same spot. The young child is learning to care for their environment, return their work when finished and to respect their materials. The low shelves are just the perfect size for infant and toddler materials and they are the right size for a toddler to learn to look after and keep tidy and organised.
Otis learnt to pull himself up and stand at the shelves. So I suggest any low shelving needs to be stable. For a toddler I was taught to put out no more than nine activities (toys, materials or trays) and rotate weekly to fortnightly and keep out the favourites. However even today when Otis is a preschooler the low shelves are still fully in use. They are so functional and really worth the effort and the cost.
Our shelves were handmade many years ago however there are other various handmade and store bought options available. I really like these shelves by Community Playthings, Kidkraft or perhaps even this one from Ikea (used horizontally). Have you invested in low shelves? Please feel free to leave a link to any good, low shelving sources or pictures of your own shelves.